bypassing censorship

bypassing censorship
Published : 2011-05-31
License : None
1. Introduction
2. About This Manual
On 10 December 1948, the adoption by the General Assembly of the Universal Declaration of
Human Rights launched a new era. Lebanese scholar Charles Habib Malik described it to the
assembled delegates as follows:
Every member of the United Nations has solemnly pledged itself to achieve respect for
and observance of human rights. But, precisely what these rights are we were never
told before, either in the Charter or in any other national instrument. This is the first
time the principles of human rights and fundamental freedoms are spelled out
authoritatively and in precise detail. I now know what my government pledged itself
to promote, achieve, and observe. … I can agitate against my government, and if
she does not fulfill her pledge, I shall have and feel the moral support of the entire
One of the fundamental rights the Universal Declaration described, in Article 19, was the right to
freedom of speech:
Everyone has the right to freedom of opinion and expression; this right includes
freedom to hold opinions without interference and to seek, receive, and impart
information and ideas through any media and regardless of frontiers.
When those words were written sixty years ago, no one imagined how the global phenomenon of
the Internet would expand people's ability to "seek, receive and impart information", not only
across borders but at amazing speeds and in forms that can be copied, edited, manipulated,
recombined and shared with small or large audiences in ways fundamentally different than the
communications media available in 1948.
The unbelievable growth in the past several years of what is on the Internet and where it is
available has the effect of making an unimaginably vast portion of human knowledge and activity
suddenly present in unexpected places: a hospital in a remote mountain village, your 12-yearold's bedroom, the conference room where you are showing your closest colleagues the new
product design that will put you ahead of the competition, your grandmother's house.
In all of these places, the possibility of connecting to the world opens up many wonderful
opportunities for improving people's lives. When you contract a rare disease on vacation, the
remote village hospital may save your life by sending your test results to a medical specialist in
the capital, or even in another country; your 12-year-old can research her school project or
make friends with kids in other countries; you can present your new product design
simultaneously to top managers in offices around the world, who can help you improve it; your
grandmother can send you her special apple pie recipe by e-mail in time for you to bake it for
dessert tonight.
But the Internet does not contain only relevant and helpful educational information, friendship
and apple pie. Like the world itself, it is vast, complex and often scary. It is just as available to
people who are malicious, greedy, unscrupulous, dishonest or merely rude as it is to you and
your 12-year-old child and your grandmother.
With all of the best and worst of human nature reflected on the Internet and certain kinds of
deception and harassment made much easier by the technology, it should not surprise anyone
that the growth of the Internet has been paralleled by attempts to control how people use it.
There are many different motivations for these attempts. The goals include:
Protecting children from material perceived as inappropriate, or limiting their contact with
people who may harm them.
Reducing the barrage of unwanted commercial offers by e-mail or on the Web.
Controlling the size of the flow of data any one user is able to access at one time.
Preventing employees from sharing information that is viewed as the property of their
employer, or from using their work time or an employer's technical resources for personal
Restricting access to materials or online activities that are banned or regulated in a specific
jurisdiction (for example a country or an organization like a school) such as explicit sexual
or violent materials, drugs or alcohol, gambling and prostitution, and information about
religious, political or other groups or ideas that are deemed to be dangerous.
Some of these concerns involve allowing people to control their own experience of the Internet
(for instance, letting people use spam-filtering tools to prevent spam from being delivered to
their own e-mail accounts), but others involve restricting how other people can use the Internet
and what those other people can and can't access. The latter case causes significant conflicts and
disagreements when the people whose access is restricted don't agree that the blocking is
appropriate or in their interest.
The kinds of people and institutions who try to restrict the Internet use of specific people are as
varied as their goals. They include parents, schools, commercial companies, operators of Internet
cafés or Internet Service Providers (ISPs), and governments at different levels.
The extreme end of the spectrum of Internet control is when a national government attempts to
restrict the ability of its entire population to use the Internet to access whole categories of
information or to share information freely with the outside world. Research by the OpenNet
Initiative ( has documented the many ways that countries filter and block
Internet access for their citizens. These include countries with pervasive filtering policies, who
have been found to routinely block access to human rights organizations, news, blogs, and Web
services that challenge the status quo or are deemed threatening or undesirable. Others block
access to single categories of Internet content, or intermittently to specific websites or network
services to coincide with strategic events, such as elections or public demonstrations. Even
countries with generally strong protections for free speech sometimes try to limit or monitor
Internet use in connection with suppressing pornography, so-called "hate speech", terrorism and
other criminal activities, leaked military or diplomatic communications, or the infringement of
copyright laws.
Any of these official or private groups may also use various techniques to monitor the Internet
activity of people they are concerned about, to make sure that their attempts at restriction are
working. This ranges from parents looking over their child's shoulder or looking at what sites
were visited on the child's computer, to companies monitoring employees' e-mail, to law
enforcement agencies demanding information from ISPs or even seizing the computer in your
home looking for evidence that you have engaged in "undesirable" activities.
Depending on who is restricting access to the Internet and/or monitoring its use, and the
perspective of the person whose access is being restricted, nearly any of these goals and any of
the methods used to achieve them may be seen as legitimate and necessary or as unacceptable
censorship and a violation of fundamental human rights. A teenage boy whose school blocks
access to his favorite online games or to social networking sites such as Facebook feels his
personal freedom to be abridged just as much as someone whose government prevents him
from reading an online newspaper about the political opposition.
Who is able to restrict access to the Internet on any given computer in any given country
depends on who has the ability to control specific parts of the technical infrastructure. This
control may be based on legally established relationships or requirements, or on the ability of
governmental or other bodies to pressure those who have legal control over the technical
infrastructure to comply with requests to block, filter or collect information. Many parts of the
international infrastructure that supports the Internet are under the control of governments or
government-controlled agencies, any of which may assert control, in accordance with local law or
Filtering or blocking of parts of the Internet may be heavy-handed or very light, clearly defined or
nearly invisible. Some countries openly admit to blocking and publish blocking criteria, as well as
replacing blocked sites with explanatory messages. Other countries have no clear standards and
sometimes rely on informal understandings and uncertainty to pressure ISPs to filter. In some
places, filtering comes disguised as technical failures and governments don't openly take
responsibility or confirm when blocking is deliberate. Different network operators even in the
same country and subject to the same regulations may execute filtering in quite different ways
out of caution, technical ignorance, or commercial competition.
At all levels of possible filtering, from individual to national, the technical difficulties of blocking
precisely what is viewed as undesirable may have unexpected and often ridiculous consequences.
"Family-friendly" filters meant to block sexual materials prevent access to useful health
information. Attempts to block spam may filter out important business correspondence.
Attempts to block access to specific news sites may also cut off educational resources.
Just as many individuals, corporations and governments see the Internet as a source of
dangerous information that must be controlled, there are many individuals and groups who are
working hard to ensure that the Internet, and the information on it, is freely available to
everyone who wants it. These people have as many different motivations as those seeking to
control the Internet. However, for someone whose Internet access is restricted and who wants
to do something about it, it may not matter whether the tools were developed by someone who
wanted to chat with a girlfriend, write a political manifesto, or send spam.
There is a vast amount of energy, from commercial, non-profit and volunteer groups, devoted to
creating tools and techniques to bypass Internet censorship, resulting in a number of methods to
bypass Internet filters. Collectively, these are called circumvention methods, and can range
from simple work-arounds, protected pathways, to complex computer programs. However, they
nearly all work in approximately the same manner. They instruct your Web browser to take a
detour through an intermediary computer, called a proxy, that:
is located somewhere that is not subject to Internet censorship
has not been blocked from your location
knows how to fetch and return content for users like you.
Only you, the person who hopes to bypass restrictions on your Internet access, can decide
whether there are significant risks involved in accessing the information you want; and only you
can decide whether the benefits outweigh the risks. There may be no law specifically banning the
information you want or the act of accessing it. On the other hand, the lack of legal sanctions
does not mean you are not risking other consequences, such as harassment, losing your job, or
The following chapters discuss how the Internet works, describe various forms of online
censorship, and elaborate on a number of tools and techniques that might help you circumvent
these barriers to free expression. The overarching issue of digital privacy and security is
considered throughout the book, which begins by covering the basics, then addresses a few
advanced topics before closing with a brief section intended for webmasters and computer
specialists who want to help others bypass Internet censorship.
This manual, 'Bypassing Internet Censorship', provides an introduction to the topic and explains
some of the software and methods most often used for circumventing censorship. There is some
information on avoiding surveillance and other means of detection while bypassing censorship,
however this is a large topic in itself so we have only addressed it where it coincides directly with
issues of circumvention.
A full discussion of techniques for maintaining anonymity and preventing detection of content or
activities is beyond the scope of this book.
The first version of this manual featured content that had been largely written at a Book Sprint
that took place in November 2008 in the beautiful hills of Upper New York State in the USA.
Eight people worked together over an intensive five-day period to produce the book.
The updated version of this manual that you are currently reading was compiled in the context
of a second Book Sprint held near Berlin, Germany, in early 2011. This time, 11 people worked
together over an intensive five-day period.
This book is a living document of course and is available online for free, where you can also edit
it and improve it.
In addition to the material written during the two Book Sprints, material has been contributed
from previous publications. These include contributions from:
Ronald Deibert
Ethan Zuckerman
Roger Dingledine
Nart Villeneuve
Steven Murdoch
Ross Anderson
Freerk Ohling
Frontline Defenders
Hal Roberts, Ethan Zuckerman, Jillian York, Robert Faris, and John Palfrey from The
Berkman Center for Internet & Society at Harvard University
These writers kindly agreed to let us use their material within a GPL licensed environment.
This manual has been written within FLOSS Manuals. To improve this manual follow these steps:
Register at FLOSS Manuals:
Select the manual ( and a chapter to
work on.
If you need to ask us questions about how to contribute then join the chat room listed below and
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3. Quickstart
The Internet is censored when the people or groups controlling a network prevent Internet users
from accessing particular content or services.
Internet censorship takes many forms. For example, governments may block regular e-mail
services in order to compel citizens to use government e-mail that can be easily monitored,
filtered, or shut down. Parents can control the content their minor children access. A university
may prevent students from accessing Facebook from the library. An Internet caf owner can
block peer-to-peer file sharing. Authoritarian governments may censor reports on human rights
abuses or the last stolen election. People have widely varying views about the legitimacy or
illegitimacy of these forms.
Circumvention is the act of bypassing Internet censorship. There are many ways to do this, but
nearly all circumvention tools work in approximately the same manner. They instruct your Web
browser to take a detour through an intermediary computer, called a proxy, that:
is located somewhere that is not subject to Internet censorship
has not been blocked from your location
knows how to fetch and return content for users like you.
Keep in mind that no tool is a perfect solution for your situation. Different tools offer varying
degrees of security, but technology cannot eliminate the physical risks you take by opposing
people in power. This book contains several chapters explaining how the Internet works which is
important for understanding how to be safer while circumventing censorship.
Some tools only work with your Web browser, while others might be applied to several programs
at once. These programs might need to be configured to send Internet traffic through a proxy.
With a little extra patience, you can do all of this without installing any software on your
computer. Note that tools that fetch Web pages for you may not display the site correctly.
Some tools use more than one intermediary computer in order to hide the fact that you are
visiting blocked services. This also hides your activities from the tool provider, which can be
important for anonymity. A tool may have a clever way of learning about alternative proxies it
may connect to in case the one you are using gets censored itself. Ideally, the traffic created by
all of this requesting, fetching and sending is encrypted in order to protect it from prying eyes.
But choosing the right tool for your particular situation is almost certainly not the most
important decision you will make when it comes to accessing or producing content in the face of
Internet censorship. Though it is difficult to provide concrete advice on such things, it is crucial to
spend your time thinking about context, such as:
how, when, and where you intend to use these tools
who might want to prevent you from doing the things the tools allow you to do
how strongly those organizations and individuals oppose this usage
what resources they have at their disposal to help them achieve their desired outcome, up
to and including violence.
The most basic type of circumvention tool is a Web proxy. While there are many reasons why it
might not be the optimal solution for you, for very basic circumvention purposes it is often a
good place to start. Assuming it has not yet been blocked from your location, visit the following
URL bar:
Press Enter or click GO, and if it successfully navigates to the requested website then it is
working. If the link above does not work, you will have to find an alternative circumvention
method. The Web proxy and Psiphon chapters of this book offer a little advice about finding a
Web proxy and a lot of advice about deciding whether or not you should be willing to use it once
you do.
If you need access to the full feature set of a particularly complex Web site such as Facebook
you might want to use a simple, installable tool like Ultrasurf instead of a Web proxy. If you
desire or require a solution that has been through rigorous security testing and that can help you
remain anonymous without requiring that you know who actually administers the service itself,
you should use Tor. If you need access to filtered Internet resources other than just Web sites,
such as blocked instant messaging platforms or filtered email servers (the kind used by programs
like Mozilla Thunderbird or Microsoft Outlook), you might try HotSpot Shield or some other
OpenVPN service. All of these tools, which have their own chapter later in the book, are briefly
described below.
Ultrasurf is a free proxy tool for the Windows operating system which can be downloaded at, or The
downloaded zip file has to be extracted with a right click and selecting "Extract All...". The
resulting .exe file can be started directly (even from a USB flash drive in an Internet caf) without
Ultrasurf connects automatically and will launch a new instance of the Internet Explorer Web
browser which you can use to open blocked Web sites.
Tor is a sophisticated network of proxy servers. It is free open source software developed
primarily to allow anonymous Web browsing, but it is also a great censorship circumvention tool.
The Tor Browser Bundle for Windows, Mac OS X or GNU/Linux can be downloaded from If the Web site is blocked
for you, you may find other download locations by typing "tor mirror" in your favorite Web
search engine or by sending an email to [email protected] with "help" in the message body.
When you click on the downloaded file, it will extract itself to the location you choose. This may
also be a USB flash drive which can be used in an Internet caf. You can then launch Tor by
clicking "Start Tor Browser" (make sure you close any Tor or Firefox instances that are already
running). After a few seconds, Tor automatically launches a special version of the Firefox Web
browser with a test Web site. If you see the green message "Congratulations. Your browser is
configured to use Tor." you can then use that window to open blocked Web sites.
If you want to access Internet services other than the Web, such as e-mail through an e-mail
client like Outlook or Thunderbird, one easy and secure way is to use a virtual private network
(VPN). A VPN will encrypt and tunnel all Internet traffic between yourself and another computer,
so not only will it make all your various kinds of traffic appear similar to an eavesdropper, but
the encryption will make it unreadable to anyone along the way. While connecting with the VPN,
your ISP will not see your content, but will be able to see that you are connecting to the VPN.
Since many international companies use VPN technology to securely connect their remote
offices, VPN technology is unlikely to be blocked as a whole.
Hotspot Shield
An easy way to get started with VPNs is to use Hotspot Shield. Hotspot Shield is a free (but
commercial) VPN solution available for the Microsoft Windows and Mac OS X operating systems.
To install Hotspot Shield you must download the software from
The file size is about 6MB, so on a slow dial-up connection the download might take 25 minutes
or more. To install, double-click the downloaded file and follow the steps presented by the
installation wizard.
Once the installation is complete, start Hotspot Shield from the "Hotspot Shield Launch" icon on
your desktop or via "Programs > Hotspot Shield". A browser window will open with a status page
showing different stages of the connection attempt such as "Authenticating" and "Assigning IP
address". Once connected, Hotspot Shield will redirect you to a welcome page. Click on "start" to
begin surfing.
To stop Hotspot Shield, right click on the traybar icon and select "Disconnect/OFF".
4. How the Net Works
5. Censorship and the Net
6. Circumvention and Safety
Imagine a group of individuals who decide to share information on their computers by connecting
them, and by sending information between these computers. Their efforts result in a set of
devices able to communicate with each other via a computer network. Of course, the network
can be even more valuable and useful if it is connected to other networks and hence to other
computers and network users. This simple desire to connect and share information electronically
is manifested today in the global Internet. As the Internet has grown rapidly, the complexity of
its interconnections has also increased, and the Internet is literally built up from the
interconnection of a tremendous number of networks.
The fundamental task of the Internet can be described as facilitating the journey of digital
information from its origin to its destination, using a suitable path and an appropriate mode of
Local computer networks, called Local Area Networks, or LANs, physically connect a number of
computers and other devices at the same physical location to one another. They can also
connect to other networks via devices called routers that manage the information flow between
networks. Computers in a LAN can communicate with each other directly for purposes like
sharing files and printers, or playing multi-player networked video games. A LAN could be useful
even if it were not connected to the outside world, but it clearly becomes more useful when it is.
The Internet today is a decentralized world-wide network of such local computer networks, as
well as larger networks such as university and corporate networks, and the networks of hosting
The organizations that arrange these interconnections between networks are called Internet
Service Providers or ISPs. An ISP's responsibility is to deliver data to the appropriate place,
usually by forwarding the data to another router (called "the next hop") closer to the data's final
destination. Often, the next hop actually belongs to a different ISP.
In order to do this, the ISP may purchase its own Internet access from a larger ISP, such as a
national provider. (Some countries have only a single national-level provider, perhaps
government-operated or government-affiliated, while others have several, which might be
competing private telecommunications firms.) National providers may similarly receive their
connections from one of the multinational companies that maintain and operate the servers and
connections that are often mentioned as the backbone of the Internet.
The backbone is made up of major network equipment installations and global connections
between them via fiber-optic cables and satellites. These connections enable communications
between Internet users in different countries and continents. National and international providers
connect to this backbone through routers sometimes known as gateways, which are connections
that allow disparate networks to communicate with each other. These gateways, just like other
routers, may be a point at which Internet traffic is monitored or controlled.
The creators of the Internet generally believed that there is only one Internet, that it is global,
and that it should allow any two computers anywhere in the world to communicate directly with
one another, assuming the owners of both computers want this to happen.
In a 1996 memo, Brian Carpenter, then chairman of the Internet Architecture Board, wrote:
in very general terms, the [Internet engineering] community believes
that the goal is connectivity ... [the] growth of the network seems
to show that connectivity is its own reward, and is more valuable than
any individual application.
There is still a major community of Internet pioneers and early adopters who champion the
ideals of worldwide interconnectivity, open standards, and free access to information, although
these ideals often come into conflict with political and business interests and thus don't always
directly influence the day-to-day operating practices and policies of individual parts of the
The originators of the Internet also created and continue to create standards aimed to make it
easier for others to also create their own networks, and to join them to each other.
Understanding Internet standards helps make clear how the Internet works and how network
sites and services become accessible or inaccessible.
Most LANs today are built with wired Ethernet or with wireless Ethernet (802.11 or Wi-Fi)
technology. All of the interconnections (of LANs and other devices) that make up the Internet
use common technical standards, or Internet protocols, to let computers find and communicate
with to one another. Often, the interconnections use privately-owned equipment and facilities,
and are operated on a for-profit basis. In some jurisdictions, Internet connections are extensively
regulated by law. In others, there is little or no regulation.
The most basic standard that unites all of the devices on the global Internet is called the Internet
Protocol (IP).
When your computer connects to the Internet, it is normally assigned a numeric IP address. Like
a postal address, the IP address uniquely identifies a single computer on the Internet. Unlike the
postal address, however, an IP address (particularly for a personal computing device) is not
necessarily permanently associated with a specific computer. So, when your computer
disconnects from the Internet and reconnects at a later time, it may receive a different (unique)
IP address. The IP protocol version currently in predominant use is IPv4. In the IPv4 protocol, an
IP address is written as four numbers in the range 0-255, separated by dots (e.g.
All Internet servers, such as those which host Web sites, also have IP addresses. For example,
the IP address of is Since remembering IP addresses is
cumbersome and IP addresses might change over time, specific systems are in place to make it
easier for you to reach your destination on the Internet. This system is the Domain Name
System (DNS), where a set of computers are dedicated to serving your computer with the IP
addresses associated with the human-memorable "names".
For example, to access the Witness Web site you would type in the address,
also known as a domain name, instead of Your computer then sends a message
with this name to a DNS server. After the DNS server translates the domain name into an IP
address, it shares that information with your computer. This system makes Web browsing and
other Internet applications more human-friendly for humans, and computer-friendly for
Mathematically speaking, IPv4 allows for a pool of about 4.2 billion different computers to be
connected to the Internet. There is also technology that lets multiple computers share a single IP
address. Despite this, the pool of available addresses was more or less exhausted at the
beginning of 2011. As a result, the IPv6 protocol has been devised, with a much larger repository
of possible unique addresses. IPv6 addresses are much longer, and even harder to remember,
than traditional IPv4 addresses. An example of an IPv6 address is:
Although as of 2011 less than 1% of the Internet uses the IPv6 protocol, this will probably change
dramatically in the near future.
The information you exchange as you use the Internet could take many forms:
an e-mail to your cousin
a picture or video of an event
a database of contact information
a file containing a set of instructions
a document containing a report on a sensitive topic
a computer program that teaches a skill.
There is a wide variety of Internet software to accommodate proper handling of the various
forms of information according to specific protocols, such as:
e-mail via Simple Mail Transport Protocol (SMTP)
instant messaging via Extensible Messaging and Presence Protocol (XMPP)
file sharing via File Transfer Protocol (FTP),
peer-to-peer file sharing via BitTorrent protocol
Usenet news via Network News Transfer Protocol (NNTP)
a combination of protocols: voice communication using Voice Over Internet Protocol (VoIP),
Session Initiation Protocol (SIP) and Real-time Transport Protocol (RTP)
Although many people use the terms "the Internet" and "the Web" interchangeably, actually the
Web refers to just one way of communicating using the Internet. When you access the Web, you
do so using software called a Web browser, such as Mozilla Firefox, Google Chrome, Opera, or
Microsoft Internet Explorer. The protocol that the Web operates on is called the Hyper-Text
Transfer Protocol or HTTP. You might also have heard of HTTPS, which is the secure version of
HTTP that uses Transport Layer Security (TLS) encryption to protect your communications.
Let's follow the example of visiting a Web site from your home computer.
Connecting to the Internet
To connect your computer to the Internet, you may need some extra equipment, such as a
modem or a router, to first connect to your ISP's network. Usually, end-user computers or home
networks are connected with ISPs via one of several technologies:
telephone modem ("dial-up"), sending Internet data over telephone lines in the form of a
telephone call
DSL, a more efficient and higher-speed way to send data over telephone lines over short
cable modem (or "cable Internet"), sending Internet data over a cable television company's
coaxial cable
fiber-optic cables, particularly in densely-populated areas of developed countries
wide-area fixed wireless links, particularly in rural areas
data service over the mobile phone network.
Browse to the Web site
1. You type in The computer sends the domain name
"" to a selected DNS server, which returns a message containing the
IP address for the Tactical Tech Security in a Box Web server (currently,
2. The browser then sends a request for a connection to that IP address.
3. The request goes through a series of routers, each one forwarding a copy of the request
to a router closer to the destination, until it reaches a router that finds the specific
computer needed.
4. This computer sends information back to you, allowing your browser to send the full URL
and receive the data to display the page.
The message from the Web site to you travels through other devices (computers or routers).
Each such device along a path can be referred to as a "hop"; the number of hops is the number
of computers or routers your message comes in contact with along its way and is often between
5 and 30.
Normally all of these complex processes are hidden and you don't need to understand them in
order to find the information you need. However, when people or organizations attempting to
limit your access to information interfere with the operation of the system, your ability to use
the Internet may be restricted. In that case, understanding just what they have done to
interfere with your access can become extremely relevant.
Consider firewalls, which are devices that intentionally prevent certain kinds of communication
between one computer and another. Firewalls help a network owner enforce policies about what
kinds of communication and use of a network are allowed. Initially, the use of firewalls was
conceived as a computer security measure, because they can help repel electronic attacks
against inadvertently misconfigured and vulnerable computers. But firewalls have come to be
used for a much wider range of purposes and for enforcing policies far beyond the purview of
computer security, including content controls.
Another example is DNS servers, which were described as helping provide IP addresses
corresponding to requested domain names. However, in some cases, these servers can be used
as censoring mechanisms by preventing the proper IP address from being returned, and
effectively blocking access to the requested information from that domain.
Censorship can occur at different points in the Internet infrastructure, covering whole networks,
domains or subdomains, individual protocols, or specific content identified by filtering software.
The best method to avoid censorship will depend on the specific censorship technique used.
Understanding these differences will help you to choose appropriate measures for you to use the
Internet effectively and safely.
In order to share data and resources, computers need to agree on conventions about how to
format and communicate information. These conventions, which we call protocols, are
sometimes compared to the grammar of human languages. The Internet is based on a series of
such protocols.
The layered networking model
Internet protocols rely on other protocols. For example, when you use a Web browser to access
a Web site, the browser relies on the HTTP or HTTPS protocol to communicate with the Web
server. This communication, in turn, relies on other protocols. Suppose we are using HTTPS for a
particular Web site to ensure that we access it securely.
In the above example, the HTTPS protocol relies on the TLS protocol to perform encryption of
the communications so that they are private and unmodified as they travel across the network.
The TLS protocol, in turn, relies on the TCP protocol to ensure that information is not
accidentally lost or corrupted in transmission. Finally, TCP relies on the IP protocol to ensure that
data is delivered to the intended destination.
While using the encrypted HTTPS protocol, your computer still uses the unencrypted DNS
protocol for retrieving an IP address for the domain name. The DNS protocol uses the UDP
protocol to mark the request for proper routing to a DNS server, and UDP relies on IP for actual
transmission of data to the intended destination.
Because of this hierarchical protocol relationship, we often refer to network protocols as existing
in a set of layers. A protocol at each layer is responsible for a particular aspect of the
communications functionality.
Using Ports
Computers connect to each other via the TCP protocol mentioned above and stay connected for
a period of time to allow higher-level protocols to carry out their tasks. TCP uses a concept of
numbered ports to manage these connections and distinguish connections from one another.
The use of numbered ports also allows the computer to decide which particular software should
handle a specific request or piece of data. (UDP also uses port numbers for this purpose.)
The IANA (Internet Assigned Names Authority) assigns port numbers for various higher-level
protocols used by application services. A few common examples of the standard assigned port
numbers are:
20 and 21 - FTP (file transfer)
22 - SSH (secure shell remote access)
23 - Telnet (insecure remote access)
25 - SMTP (send e-mail)
53 - DNS (resolves a computer's name to an IP address)
80 - HTTP (normal Web browsing; also sometimes used for a proxy)
110 - POP3 (receive e-mail)
143 - IMAP (send/receive e-mail)
443 - HTTPS (secure Web connections)
993 - secure IMAP
995 - secure POP3
1080 - SOCKS proxy
1194 - OpenVPN
3128 - Squid proxy
8080 - Standard HTTP-style proxy
Using these particular numbers is not generally a technical requirement of the protocols; in fact,
any sort of data could be sent over any port (and using non standard ports can be a useful
circumvention technique). However, these assignments are used by default, for convenience. For
example, your Web browser knows that if you access a Web site without specifying any port
number, it should automatically try using port 80. Other kinds of software have similar defaults
so that you can normally use Internet services without knowing or remembering the port
numbers associated with the services you use.
Cryptography is a form of technical defense against surveillance that uses sophisticated
mathematical techniques to scramble communications, making them unintelligible to an
eavesdropper. Cryptography can also prevent a network operator from modifying
communications, or at least make such modifications detectable. It usually works like a tunnel
from the software you are using, such as a Web browser, to the other end of the connection,
such as a Web server.
Modern cryptography is thought to be extremely difficult to defeat by technical means; widely
available cryptographic software can give users very powerful privacy protection against
eavesdropping. On the other hand, encryption can be circumvented by several means, including
targeted malware, or in general through key-management and key-exchange problems, when
users cannot or do not follow the procedures necessary to use cryptography securely. For
example, cryptographic applications usually need a way to verify the identity of the person or
computer at the other end of a network connection; otherwise, the communication could be
vulnerable to a man-in-the-middle attack where an eavesdropper impersonates one's
communication partner in order to intercept supposedly private communications. This identity
verification is handled in different ways by different software, but skipping or bypassing the
verification step can increase one's vulnerability to surveillance.
Another surveillance technique is traffic analysis, where facts about a communication are used
to infer something about its content, origin, destination, or meaning even if an eavesdropper is
unable to understand the contents of the communication. Traffic analysis can be a very powerful
technique and is very difficult to defend against; it is of particular concern for anonymity
systems, where traffic analysis techniques might help identify an anonymous party. Advanced
anonymity systems like Tor contain some measures intended to reduce the effectiveness of
traffic analysis, but might still be vulnerable to it depending on the capabilities of the
Understanding how the Internet is controlled in practice can help to relate the sources of
Internet censorship to the possible threats. Internet controls and censorship can be wide-ranging.
A national government might not only block access to content, but also monitor what
information people in its country are accessing, and might penalize users for Internet-related
activities that the government deems unacceptable. Governments may both define what to
block and carry out the blocking, or they may create legislation, regulations, or extra-legal
incentives to compel the staff of nominally independent companies to carry out blocking and
The full story of Internet governance is complicated, political and still being actively disputed.
Governments often have the authority and resources to implement their preferred schemes of
Internet monitoring and control, whether Internet infrastructure is owned and operated by
governments themselves or by private telecommunications companies. So a government that
wants to block access to information can often readily exercise direct or indirect control over
points where that information is produced, or where it enters or exits the country.
Governments also have extensive legal authority to spy on citizens, and many go behind what
the law allows, using extra-legal methods to monitor or restrict Internet use and reshape it
according to their own rules.
The Internet was developed by U.S. government-sponsored research during the 1970s. It
gradually spread to academic use, then to business and public use. Today, a global community is
working to maintain the standards and agreements that attempt to achieve world-wide open
connectivity and interoperability without any geographical distinction.
However, governments are not compelled to implement Internet infrastructure in accordance
with these goals or related recommendations about Internet architecture. Some governments
design their national telecommunications systems to have single "choke points" where they can
control their whole country's access to specific sites and services, and in some cases prevent
access to their section of the Internet from outside.
Other governments have passed laws or adopted informal controls to regulate the behavior of
private ISPs, sometimes compelling them to participate in surveillance or blocking or removing
access to particular materials.
Some of the Internet's facilities and coordinating functions are managed by governments or by
corporations under government charter. There is no international Internet governance that
operates entirely independently. Governments treat the ability to control Internet and
telecommunications infrastructure as matters of national sovereignty, and many have asserted
the right to forbid or block access to certain kinds of content and services deemed offensive or
Many governments have a problem with the fact that there is only one global Internet with
technically no geographic or political borders. For the end-user, it makes (apart from a delay of a
few milliseconds) no difference if a Web site is hosted in the same country or on the other side
of the world a reality often delightful for Internet users and deeply alarming for states. Internet
censorship, inspired by hopes of re-imposing geography and geographic distinctions, can occur for
many reasons.
Adapting a classification from the Open Net Initiative (, we can describe some
of these reasons as:
Political reasons
Governments want to censor views and opinions contrary to the respective country's
policies including topics such as human rights and religions.
Social reasons
Governments want to censor Web pages related to pornography, gambling, alcohol, drugs
and other subjects that might seem offensive for the population.
National security reasons
Governments want to block content related to dissident movements, and anything
threatening national security.
In order to ensure that information controls are effective, governments may also filter tools that
enable people to bypass Internet censorship.
In the extreme case, governments can refuse to provide Internet service to the public, as in
North Korea, or can cut off the Internet throughout their territory during periods of public
protest, as happened briefly in Nepal in 2005, and in Egypt and Libya in 2011.
Control can be aimed at both access providers and content providers.
Governments can submit access providers to strict control, in order to regulate and shape
Internet traffic, and enable surveillance and monitoring upon Internet users within the
country. This is also a means to block global content that has been made available from
abroad. For example, the Pakistani government asked local ISPs to block access to
Facebook in May 2010 in order to block access to caricatures of the Prophet Muhammad
that had been made available on the social networking site, as they had no control over
the content provider Facebook.
Governments can request content providers, such as in-country Web site editors,
Webmasters or search engines to forbid and block access to certain kinds of content and
services deemed offensive or dangerous. For example, local Google subsidiaries have been
requested to remove controversial content in a couple of countries (such as in China,
before March 2010, when it redirected search engine activities towards Google Hong Kong).
In general, it can be difficult to determine whether someone is preventing you from accessing a
Web site or from sending information to others. When you try to access a blocked site, you may
see a conventional error message or nothing at all. The behavior may make it look like the site is
inaccessible for technical reasons. The government or the ISP may deny the fact that censorship
is in place and even blame the (foreign) Web site.
Some organizations, most notably the OpenNet Initiative, are using software to test Internet
access in various countries and to understand how access may be compromised by different
parties. In some cases, this is a difficult or even dangerous task, depending on the authorities
In some countries, there is no doubt about government blocking of parts of the Internet. In Saudi
Arabia, for example, attempting to access sexually explicit material results in a noticeable
message from the government explaining that the site is blocked, and why.
In countries that block without notification, one of the most common signs of censorship is that a
large number of sites with related content are apparently inaccessible for technical reasons or
seem to be out of order (for example, "Page Not Found" errors, or connections timing out often).
Another potential indication is that search engines appear to return useless results or nothing at
all about certain topics.
Filtering or blocking is also done by entities other than governments. Parents may filter the
information that reaches their children. Many organizations, from schools to businesses, restrict
Internet access in order to prevent users from having unmonitored communications, using
company time or hardware for personal reasons, infringing copyrights, or using excessive
networking resources.
Many governments have the resources and legal ability to control large portions of a country's
network infrastructure. If the government is your adversary, keep in mind that the entire
communications infrastructure from the Internet to mobile and landline phones can be
Users in different places may have widely varying experiences of Internet content controls.
In some places, your government may be legally constrained from filtering or decide not to
filter content. You may be monitored by your ISP so the information can be sold to
advertisers. The government may have required ISPs to install monitoring (but not blocking)
capabilities in their networks. The government may make a formal request for your
browsing history and chat logs, or may store information for later use. It will try not to
attract attention as it does this. You face threats from non-government actors, such as
computer criminals who attack Web sites or steal personal financial information.
In some places, ISPs may use technical means to block some sites or services, but the
government doesn't currently appear to track or retaliate against attempts to access
them, or appear to operate a coordinated Internet content control strategy.
In some places, you may have access to local services that are a fair match for foreign
services. These services are patrolled by your ISP or government agents. You may be free
to post sensitive content, but it will be removed. If this happens too often, however, the
penalties may become more severe. Restrictions may only become obvious during
politically charged events.
In some places, your government may filter most foreign websites, especially news. It
exercises tight control over ISPs to block content and keep track of people creating
content. If you use a social networking platform, efforts will be made to infiltrate it. The
government may encourage your neighbors to spy on you.
Governments have a range of motivations for monitoring or restricting different kinds of people's
online activity.
Activists: you may want to improve your government or are seeking a new one. Perhaps
you want to reform a particular segment of society or work for the rights of minority
groups. You may want to expose environmental issues, labor abuses, fraud, or corruption
at your place of work. Your government and employers are going to be unhappy about this
no matter the time of year, but they may put more effort into monitoring you if they
suspect that there will be protests in the streets soon.
Bloggers: you may want to write about everyday life, but some people are silenced
because of ethnicity or gender. Regardless of what you have to say you're not supposed to
be saying it. You may be in a country with mostly unrestricted users, but your opinions are
not popular in your community. You might prefer anonymity or need it to connect with a
support group.
Journalists: you may have some of the same concerns as activists and bloggers. Organized
crime, corruption, and government brutality are dangerous subjects to cover. You may
need to protect yourself and any activists who become sources of information.
Readers: you may not be politically active, but so much content is censored that you need
circumvention software to get to entertainment, science, and industry periodicals. You
may want to read a Web comic or browse the news about other countries. Your
government may ignore this until it has some other reason to monitor you.
The most commonly blocked Internet resource used to be sexually explicit material; today, it is
social networking platforms. The growing international popularity of social networking sites has
turned millions of Internet users around the world into potential victims of censorship.
Some social networking sites are popular at a global level, such as Facebook, MySpace or
LinkedIn, while others have a large number of users in a given country or region: QQ (Qzone) in
China, Cloob in Iran, vKontakte in Russia, Hi5 in Peru and Colombia, Odnoklassniki in CIS
countries, Orkut in India and Brazil, Zing in Vietnam, Maktoob in Syria, Ameba and Mixi in Japan,
Bebo in the UK, and others.
[This is adapted in part from Access Denied, Chapter 3, by Steven J. Murdoch and Ross
The techniques described in this chapter are some of the methods employed by censors that try
to prevent Internet users from accessing particular content or services. Network operators can
filter or manipulate Internet traffic at any point in a network, using a wide variety of
technologies, with varying levels of accuracy and customization. Typically, these maneuvers
involve using software to look at what users are attempting to do and to interfere selectively
with activities that the operator considers forbidden by policy. A filter could be created and
applied by a national government or by a national or local ISP, or even by the operator of a local
network; or software-based filters could be installed directly onto individual computers.
The goals of deploying a filtering mechanism vary depending on the motivations of the
organization deploying them. They may be to make a particular Web site (or individual Web page)
inaccessible to those who wish to view it, to make it unreliable, or to deter users from even
attempting to access it in the first place. The choice of mechanism will also depend upon the
capability of the organization that requests the filtering what access and influence they have, the
people against whom they can enforce their wishes, and how much they are willing to spend.
Other considerations include the number of acceptable errors, whether the filtering should be
overt or covert, and how reliable it is (both against casual users and those who wish to bypass
We will describe several techniques by which particular content can be blocked once the list of
resources to be blocked is established. Building this list is a considerable challenge and a common
weakness in deployed systems. Not only does the huge number of Web sites make building a
comprehensive list of prohibited content difficult, but as content moves and Web sites change
their IP addresses, keeping this list up-to-date requires a lot of effort. Moreover, if the operator
of a site wishes to interfere with the blocking, the site could be moved more rapidly than it
would be otherwise.
We first describe technical measures used against end users, and then briefly discuss measures
used against publishers and hosting providers, as well as non-technical intimidation.
Please note that the list of methods is not exhaustive, and more than one of these tactics might
be applied in a particular case.
On modern communications networks like the Internet, censorship and surveillance (the
monitoring of people's communications or activities) are intimately connected in practice.
Most ISPs in the world monitor some aspects of their users' communications for accounting
purposes and to combat abuse such as spam. ISPs often record user account names together
with IP addresses. Unless users employ privacy-enhancing technologies to prevent it, it is
technically possible for an ISP to record all the information that flows over its cables, including
the exact contents of users' communications.
This surveillance is also a prerequisite for technically-based network censorship. An ISP trying to
censor communications that its users want to send has to be able to read those communications
in order to determine which ones violate its policies. Hence a core approach to reducing Internet
censorship is hiding the detailed content of communications from ISPs, both in individual cases
and by encouraging widespread use of pro-privacy technologies that hinder surveillance.
This means that technical counter-measures to network censorship often rely on using
obfuscation or encryption wherever possible in order to make it impossible for the ISP to see
exactly what content has been transferred.
This section discusses some of the specific ways that censors block content and access by
technical means.
URL filtering
One way for countries and other entities to block access to information on the Web is to
prevent access based on the URL either the entire URL or some part of it. Internet censors
often want to block specific domain names in their entirety, because they object to the content
of those domains. One of the easiest ways to block Web sites is by blocking the complete
domain name. Sometimes, authorities are more selective, blocking only certain subdomains in a
particular domain, while leaving the rest of the domain accessible. This is the case for Vietnam,
where the government blocks specific sections of a Web site (such as the Vietnamese-language
versions of the BBC and Radio Free Asia) but rarely censors content written in English.
Censors, for example, might filter only the subdomain, while leaving and unfiltered. Similarly, they might want to filter out pages containing specific types
of content while allowing access to the rest of the domain hosting those pages. One filtering
approach is to look for a directory name, such as "worldservice" to block only the BBC foreignlanguage news service at, without blocking the BBC's English-language
Web site as a whole. Censors can sometimes even block specific pages based on page names, or
search terms in queries, that suggest offensive or undesired content.
URL filtering can be performed locally, through the use of special software installed in the
computer that you are using. For example, computers in an Internet caf may all be running
filtering software that prevents certain sites from being accessed.
URL filtering can also be performed at a central point in the network, such as a proxy server. A
network can be configured not to allow users to connect directly to Web sites but instead to
force (or just encourage) all users to access those sites via a proxy server.
Proxy servers are used to relay requests, as well as temporarily storing web pages they retrieve
in a cache and delivering them to multiple users. This reduces the need for an ISP to frequently
retrieve a popularly requested page, thus saving on resources and improving delivery time.
However, as well as improving performance, an HTTP proxy can also block Web sites. The proxy
decides whether requests for Web pages should be permitted, and if so, sends the request to
the Web server hosting the requested content. Since the full content of the request is available,
individual Web pages can be filtered, based on both page names and the actual content of the
page. If a page is blocked, the proxy server could return an accurate explanation of the reason
why, or pretend that the page didn't exist or produced an error.
DNS filtering and spoofing
When you enter a URL in a Web browser, the first thing the Web browser does is to ask a DNS
(Domain Name System) server, at a known numeric address, to look up the domain name
referenced in the URL and supply the corresponding IP address.
If the DNS server is configured to block access, it consults a blacklist of banned domain names.
When a browser requests the IP address for one of these domain names, the DNS server gives a
wrong answer or no answer at all.
When the DNS server gives a meaningless answer or no answer, the requesting computer fails to
learn the correct IP address for the service it wanted to contact. Without the correct IP address,
the requesting computer cannot continue, and it displays an error message. Since the browser
does not learn the Web site's correct IP address, it is not able to contact the site to request a
page. The result is that all of the services under a particular domain name, such as all of the
pages on a particular Web server, are unavailable. In this case, deliberate blocking may wrongly
appear as a technical problem or random failure.
Similarly, a censor could force a DNS entry to point to an incorrect IP address, thus redirecting
Internet users to incorrect Web sites. This technique is called DNS spoofing, and censors can
use it to hijack the identity of a particular server and display forged Web sites or reroute the
users' traffic to unauthorized servers that could intercept their data. (In some networks, the
wrong answer would lead to a different Web server that clearly explains the nature of the
blocking that has occurred. This technique is used by censors who don't mind admitting that they
are engaged in censorship and who don't want users to be confused about what has taken
IP filtering
When data is sent over the Internet, it is grouped into small units, called packets. A packet
contains both the data being sent and information about how to send the packet, such as the IP
addresses of the computer it came from and the one it should go to. Routers are computers
that relay packets on their way from a sender to a receiver, determining where they go next. If
censors wants to prevent users from accessing specific servers, they can configure routers that
they control to drop (ignore and fail to transmit) data destined for IP addresses on a blacklist or
to return an error message for them. Filtering based solely on IP addresses blocks all services
provided by a particular server, such as both Web sites and e-mail servers. Since only the IP
address is inspected, multiple domain names that share the same IP address are also blocked,
even if only one was originally meant to be prohibited.
Keyword filtering
IP address filtering can only block communication on the basis of where packets are going to or
coming from, not what they contain. This can be a problem for the censor if it is impossible to
establish the full list of IP addresses containing prohibited content, or if an IP address contains
enough non-prohibited content to make it seem unjustifiable to totally block all communication
with it. There is a finer-grained control possible: the content of packets can be inspected for
banned keywords. As network routers do not normally examine the entire packet contents,
extra equipment may be needed; the process of examining packet contents is often called deep
packet inspection.
A communication identified as containing forbidden content may be disrupted by blocking the
packets directly or by forging a message to both of the communicating parties advising them
that the other party has terminated the conversation. Equipment that performs all of these
censoring functions and others is readily available on the market.
Alternatively, the censor can use a forced HTTP proxy, as described earlier.
Traffic shaping
Traffic shaping is a technique utilized by network managers to make a network run smoothly by
prioritizing some kinds of packets and delaying other kinds of packets that meet certain criteria.
Traffic shaping is somewhat similar to controlling vehicle traffic on a street. In general, all
vehicles (packets) have the same priority, but some vehicles are temporarily delayed by traffic
controllers or stop lights to avoid traffic jams at certain points. At the same time, some vehicles
(fire trucks, ambulances) may need to reach their destination faster, and therefore they are
given priority by delaying other vehicles. Similar logic is applicable to Internet packets that need
low latency for optimal performance (such as voice over IP, VoIP).
Traffic shaping can also be used by governments or other entities to delay packets with specific
information. If censors want to restrict access to certain services, they can easily identify
packets related to these services and increase their latency by setting their priority low. This
could give users the misleading impression that a site is inherently slow or unreliable, or it could
simply make the disfavored site unpleasant to use relative to other sites. This technique is
sometimes used against peer-to-peer file-sharing networks, such as BitTorrent, by ISPs that
disfavor file sharing.
Port blocking
Blacklisting individual port numbers restricts access to individual services on a server, such as
Web or e-mail. Common services on the Internet have characteristic port numbers. The
relationships between services and port numbers are assigned by IANA, but they are not
mandatory. These assignments allow routers to make a guess as to the service being accessed.
Thus, to block just the Web traffic to a site, a censor might block only port 80, because that is
the port typically used for Web access.
Access to ports may be controlled by the network administrator of the organization that hosts
the computer you're using whether a private company or an Internet caf, by the ISP that is
providing Internet access, or by someone else such as a government censor who has access to
the connections that are available to the ISP. Ports may also be blocked for reasons other than
pure content censorship to reduce spam, or to discourage disfavored network uses such as
peer-to-peer file sharing, instant messaging, or network gaming.
If a port is blocked, all traffic on this port becomes inaccessible to you. Censors often block the
ports 1080, 3128, and 8080 because these are the most common proxy ports. If this is the case,
you won't be able to directly use any proxies that require use of those ports; you'll have to use
a different circumvention technique or else find or arrange for the creation of proxies that are
listening on an uncommon port.
For example, in one university, only the ports 22 (SSH), 110 (POP3), 143 (IMAP), 993 (secure IMAP),
995 (secure POP3) and 5190 (ICQ instant messaging) may be open for external connections,
forcing users to use circumvention technology or access services on nonstandard ports if they
want to use other Internet services.
Internet shutdown
Shutting down Internet connectivity is an example of extreme censorship perpetrated by
governments in response to sensitive political and social events. However, complete network
disruption (i.e. from both domestic and international networks) requires intense work, since it is
necessary to shut down not only the protocols that connect the country to the international
network but also the protocols that connect ISPs with one another and with users. Countries
have shut down Internet access completely (Nepal in 2005, Burma in 2007 and Egypt and Libya
in 2011) as a means to quell political unrest. These shutdowns lasted from a few hours to several
weeks, though some people managed to connect through dial-up to an ISP abroad or by using
mobile connections or satellite links.
Breaking international connections, therefore, does not necessarily destroy connectivity among
domestic ISPs or communication among various users of a single ISP. It would take further steps
to completely isolate users from an internal network. For this reason, it is harder to disrupt local
interconnectivity in countries with several ISPs.
Censors can also try to suppress content and services at their source by attacking the
publishers' ability to publish or host information. This can be accomplished in several ways.
Legal restrictions
Sometimes, legal authorities can induce service operators themselves to perform or cooperate
with censorship. Some blog hosts or e-mail providers, for example, may decide to perform
keyword filtering within their own servers perhaps because governments told them to. (In this
case, there's little hope that any sort of "circumvention" will counteract these services'
censorship; we generally conceive of circumvention as an effort to reach desired network
services somewhere else, such as in a different country or jurisdiction.)
Denial of service
Where the organization deploying the filtering does not have the authority (or access to the
network infrastructure) to add conventional blocking mechanisms, Web sites can be made
inaccessible by overloading the server or network connection. This technique, known as a Denialof-Service (DoS) attack, could be mounted by one computer with a very fast network
connection; more commonly, a large number of computers are taken over and used to mount a
distributed DoS (DDoS).
Domain deregistration
As mentioned earlier, the first stage of a Web request is to contact the local DNS server to find
the IP address of the desired location. Storing all domain names in existence would be unfeasible,
so instead so-called "recursive resolvers" store pointers to other DNS servers that are more
likely to know the answer. These servers will direct the recursive resolver to further DNS
servers until one, the "authoritative" server, can return the answer.
The domain name system is organized hierarchically, with country domains such as ".uk" and
".de" at the top, along with the nongeographic top-level domains such as ".org" and ".com". The
servers responsible for these domains delegate responsibility for subdomains, such as, to other DNS servers, directing requests for these domains there. Thus, if the
DNS server for a top-level domain deregisters a domain name, recursive resolvers will be unable
to discover the IP address and so make the site inaccessible.
Country-specific top-level domains are usually operated by the government of the country in
question, or by an organization appointed by it. So if a site is registered under the domain of a
country that prohibits the hosted content, it runs the risk of being deregistered.
Server takedown
Servers hosting content must be physically located somewhere, as must the administrators who
operate them. If these locations are under the legal or extra-legal control of someone who
objects to the content hosted, the server can be disconnected or the operators can be required
to disable it.
Censors may also try to deter users from even attempting to access banned material in various
The above mechanisms inhibit the access to banned material, but are both crude and possible to
circumvent. Another approach, which may be applied in parallel to filtering, is to monitor which
Web sites are being visited. If prohibited content is accessed (or attempted to be accessed) then
legal (or extra-legal) measures could be deployed as punishment.
If this fact is widely publicized, it could discourage others from attempting to access banned
content, even if the technical measures for preventing access are inadequate by themselves. In
some places, censors try to create an impression that their agents are everywhere and that
everyone is constantly being watched whether or not this really is the case.
Social Techniques
Social mechanisms are often used to discourage users from accessing inappropriate content. For
example, families may place the PC in the living room where the screen is visible to all present,
rather than somewhere more private, as a low-key way of discouraging children from accessing
unsuitable sites. A library may situate PCs so that their screens are all visible from the librarian's
desk. An Internet caf may have a CCTV surveillance camera. There might be a local law requiring
such cameras, and also requiring that users register with government-issued photo ID.
Stealing and destroying communications equipment
In some places, censors have the ability to prohibit some kinds of communications technology
entirely. In that case, they may conspicuously confiscate or seek out and destroy prohibited
communications equipment in order to send the message that its use will not be tolerated.
The type of security you need depends on your activities and their consequences. There are
some security measures that everyone should practice whether they feel threatened or not.
Some ways to be cautious online require more effort, but are necessary because of severe
restrictions on Internet access. You may be facing threats from technology that is being
researched and deployed rapidly, old technology, use of human intelligence instead, or a
combination of all three. All of these factors may change often.
There are steps that everyone with a computer should take to keep it secure. This may involve
protecting information about your network of activists or it could be your credit card number,
but some of the tools you need are the same.
Beware of programs that promise perfect security: online safety is a combination of good
software and human behavior. Knowing what should be kept offline, who to trust, and other
security questions cannot be answered by technology alone. Look for programs that list risks on
their Web sites or have been peer reviewed.
Keep your operating system up-to-date: the developers of operating systems provide updates
that you should install from time to time. These may be automatic or you may have to request
them by entering a command or adjusting your system settings. Some of these updates make
your computer more efficient and easier to use, and others fix security holes. Attackers learn
about these security holes rapidly, sometimes even before they're fixed, so fixing them promptly
is crucial.
If you're still using Microsoft Windows, use anti-virus software and keep it updated. Malware is
software written in order to steal information or to use your computer for other purposes.
Viruses and malware can gain access to your system, make changes and hide themselves. They
could be sent to you in an e-mail, be on a Web page you visit, or be part of a file that does not
appear to be suspicious. Anti-virus software providers constantly research emerging threats and
add them to lists of things that your computer will block. In order to allow the software to
recognize new threats, you must install updates as they are released.
Use good passwords: no password selection system can guard against being threatened with
violence, but you can improve your security by making it harder to guess. Use combinations of
letters, punctuation, and numbers. Combine lower and upper case letters. Do not use birthdates,
telephone numbers, or words that can be guessed by going through public information about you.
Use Free and Open Source Software (FOSS). Open source software is made available both as a
working product and as a work in progress to users and software engineers. This offers several
security advantages over closed source, for-profit software that may only be available in your
country through illegal channels due to export restrictions or expense. You may not be able to
download official updates for pirated software. With Open Source software there is no need to
search through several suspicious sites for a copy free of spyware and security glitches. Any
legitimate copy will be free and is available from the creators. If security flaws emerge, they can
be spotted by volunteers or interested users. A community of software engineers will then work
on a solution, often very quickly.
Use software that separates who you are from where you are. Every computer connected to
the Internet has an IP address. An IP address can be used to find your physical location as easily
as typing it into a public "whois" site. Proxies, VPNs and Tor route your traffic through one to
three computers around the world. If you are going through only one server, be aware that just
like an ISP, the proxy provider can see all of your traffic. You may trust the proxy provider more
than your ISP, but the same warnings apply to any single source of connectivity. See the sections
that cover proxies, Tor, and VPNs for more on risks.
Use live CDs and bootable USB drives. If you are using a public computer or another computer on
which you do not want to leave data, use a version of Linux that you can run from portable
media. A Live CD or bootable USB drive can be plugged into a computer and used without
installing anything.
Use "portable" programs: there are also portable versions of circumvention software that can be
run under Windows from a USB drive.
Keep yourself updated: the effort put into finding you may change. The technology that works
one day may stop working or be insecure the next day. Even if you don't need it now, know
where to find information. If the software providers you use have ways to get support, make
sure you know about them before their Web sites are blocked.
In the context of closed societies and repressive countries, monitoring becomes a major threat
for users of social networking sites, especially if they use the service to coordinate civil society
activity or engage in online activism or citizen journalism.
One central issue with social networking platforms is the amount of private data that you share
about yourself, your activities and your contacts, and who has access to it. As the technology
evolves and social networking platforms are more and more accessed through smart phones, the
disclosure of the locations of the users of a social networking platform at any given moment is
also becoming a significant menace.
In that context, some precautions become even more crucial; for example, you should:
edit your default privacy settings in the social networking platform
know precisely what information you are sharing with whom
make sure that you understand the default geolocation settings, and edit them if needed
only accept into your network people who you really know and trust
only accept into your network people who will be savvy enough to also protect the private
information that you share with them, or train them to do so
be aware that even the most savvy people in your network might give up information if
they are threatened by your adversary, so consider limiting who has access to which
be aware that accessing your social networking platform via a circumvention tool will not
automatically protect you from most of the threats to your privacy.
Read more in this article from Privacy Rights Clearinghouse: "Social Networking Privacy: How to
be Safe, Secure and Social":
How can you access your social networking platform when it is filtered?
As described below, using HTTPS to access Web sites is important. If your social networking
platform allows HTTPS access, you should use it exclusively, and, if possible, make it the default.
For example, on Facebook, you can edit Account Settings > Account Security > Secure Browsing
(https) to make HTTPS the default way to connect to your Facebook account. In some places,
using HTTPS may also allow you to access to an otherwise blocked service; for example, has been blocked in Burma while remained accessible.
If you want to protect your anonymity and privacy while circumventing the filtering imposed on
your social networking service, an SSH tunnel or VPN will give you stronger privacy guarantees
than a Web proxy, including against the risk of revealing your IP address. Even using an
anonymity network like Tor can be insufficient because social networking platforms make it so
easy to reveal identifying information and expose details about your contacts and social
A significant proportion of the world's population, especially in developing countries, does not
have personal access to the Internet at their homes. This can be because of the costs of having
private Internet connection at their homes, the lack of personal computer equipment, or
problems in the telecommunication or electrical network infrastructures.
For this portion of the population the only existing, convenient or affordable mean to access the
Internet is to use places where the computers are shared with several different individuals. This
includes Internet cafs, Telecenters, work stations, schools or libraries.
Potential advantages of shared computers
There are advantages to accessing the Internet on shared computers:
You may receive technical advice and assistance from other users or facility staff on how
to circumvent filtering.
Circumvention tools may already be installed and pre-configured.
Other users may share uncensored information with you through alternative, offline
If you aren't a regular user of a particular computing facility, you didn't provide identity
documents to the facility's operator, and you don't sign in online using your real name or
account information, it would be hard for anyone to track you down personally based on
your online activity.
General risks of shared computers
The fact that you access the Internet in a public space does not make it anonymous or safe for
you. It is quite often the very opposite. Some of the main threats are:
The owner of the computer, or even a person who used the computer before you, could
easily program the computer to spy on everything you do, including recording all of your
passwords. The computer can also be programmed to circumvent or nullify the protections
of any privacy and security software you use on it.
In some countries, such as Burma and Cuba, Internet caf clients are required to show their
ID or passport before using the service. This ID information can be stored and filed
together with the clients' Web browsing history.
Any data you leave on the computer you have used may be logged (browsing history,
cookies, downloaded files, etc).
Software or hardware keyloggers installed in the client's computer may record every
keystroke during your session, including your passwords, even before this information is
sent over the Internet. In Vietnam, an apparently innocuous virtual keyboard for typing
Vietnamese characters was being used by the government to monitor user activity at
Internet cafs and other public access spots.
Your screen activity may be recorded by special software that takes screenshots at
frequent intervals, monitored through CCTV cameras, or simply observed by a person (e.g.
the Internet caf manager) looking over your shoulder.
Shared computers and censorship
Besides the surveillance, users of shared computers are often offered access to a limited
Internet and have to face additional hurdles to use their favorite circumvention solution:
In some countries, such as Burma, Internet caf owners have to display posters about
banned Web content and are responsible for the enforcement censorship law inside their
Extra filtering might be implemented by Internet caf managers (client side control and
filtering), to complement filtering implemented at the ISP or national level.
Users might be pushed by the environmental restrictions to avoid visiting specific Web
sites for fear of punishment, thus enforcing self-censorship.
Computers are often configured so that users are prevented from installing any software,
including circumvention tools, or connecting any kind of devices to the USB port (such as
USB flash drives). In Cuba, authorities have begun deploying a controlling software for
Internet cafs named AvilaLink that prevents users from installing or executing specific
software or running applications from a USB flash drive.
Users may be prevented from using any other browser but Internet Explorer, to prevent
the use of privacy or circumvention Add-ons or settings for browsers such as Mozilla
Firefox or Google Chrome.
Best practices for security and circumvention
Depending on the environment in which you use your shared computer, you can try the following:
Identify the surveillance measures implemented based on the list mentioned above (CCTV,
human surveillance, keyloggers, etc.) and behave accordingly.
Run portable circumvention software from a USB flash drive.
Use an operating system on which you have control through the use of a Live CD.
Change Internet cafs often if you fear recurring surveillance, or stick to one where you
trust it is safe to connect.
Take your own laptop to the Internet caf and use it instead of the public computers.
Some filtered networks use mainly (or exclusively) keyword filtering, rather than blocking
particular sites. For example, networks might block any communication mentioning keywords
that are considered politically, religiously, or culturally sensitive. This blocking can be overt or
disguised as a technical error. For example, some networks make it look like a technical error
occurred whenever you search for something that the network operator thinks you shouldn't be
looking for. This way, users are less likely to blame the problem on censorship.
If the content of Internet communications is unencrypted, it will be visible to ISPs' network
equipment such as routers and firewalls, where keyword-based monitoring and censorship can be
implemented. Hiding the content of communications with encryption makes the task of
censorship much more difficult, because network equipment can no longer distinguish the
communications that contain forbidden keywords from those that don't.
Using encryption to keep communications confidential also prevents network equipment from
logging communications in order to analyze them and target individuals after the fact for what
they read or write.
What is HTTPS?
HTTPS is the secure version of the HTTP protocol used to access Web sites. It provides a
security upgrade for accessing Web sites by using encryption to stop eavesdropping and
tampering with the contents of your communications. Using HTTPS to access a site can prevent
network operators from knowing which part of the site you're using or what information you
sent to and received from the site. HTTPS support is already included in every popular Web
browser, so you don't need to install or add any software in order to use HTTPS.
Usually, if a site is available through HTTPS, you can access the site's secure version by entering
its address (URL) beginning with https:// instead of http://. You can also tell if you are using the
secure version of a site by looking at the address displayed in your Web browser's navigation
bar, and seeing whether it begins with https://.
Not every Web site has an HTTPS version. Indeed, perhaps less than 10% of sites do though the
sites with HTTPS versions include several of the largest and most popular sites. A Web site is
only available through HTTPS if the Web site operator deliberately configures its HTTPS version.
Internet security experts have been urging Web site operators to do this routinely, and the
number of sites with HTTPS support has been growing steadily.
If you try to access a site through HTTPS and receive an error, this doesn't always mean that
your network is blocking access to the site. It might mean that the site is simply not available in
HTTPS (to anyone). However, certain kinds of error messages are more likely to show that
someone is actively blocking or tampering with the connection, especially if you know that a site
is supposed to be available through HTTPS.
Examples of sites that offer HTTPS
Here are a few examples of popular sites that offer HTTPS. In some cases, the use of HTTPS is
optional on these sites, not mandatory, so you have to explicitly choose the secure version of
the site in order to get the benefits of HTTPS.
Site name
Insecure (HTTP) version Secure (HTTPS) version
Google Search
Windows Live Mail
(MSN Hotmail)
For example, if you make a Google search from instead of, your network operator will not be able to see what terms you searched
for, and therefore it can't block Google from answering "inappropriate" searches. (However, the
network operator could decide to block in its entirety.) Similarly, if you use
Twitter through instead of, the network operator can't
see which tweets you are reading, what tags you are searching for, what you post there, or
which account you log into. (However, the network operator could decide to block all access to using HTTPS.)
HTTPS makes use of an Internet security protocol called TLS (Transport Layer Security) or SSL
(Secure Sockets Layer). You may hear people refer to a site "using SSL" or being "an SSL site". In
the context of a Web site, this means that the site is available through HTTPS.
Using HTTPS in addition to circumvention technology
Even circumvention technologies that use encryption are not a substitute for using HTTPS,
because the purpose for which encryption is used is different.
For many kinds of circumvention technology, including VPNs, proxies, and Tor, it is still possible
and appropriate to use HTTPS addresses when accessing a blocked site through the
circumvention technology. This provides greater privacy and prevents the circumvention provider
itself from observing or recording what you do. This could be important even if you're confident
that the circumvention provider is friendly to you, because the circumvention provider (or the
network that the circumvention provider uses) could be broken into or pressured to provide
information about you.
Some circumvention technology developers like Tor strongly urge users to always use HTTPS, to
make sure that circumvention providers themselves can't spy on users. You can read more
about this issue at It's good to
get in the habit of using HTTPS whenever possible, even when using some other method for
Tips for using HTTPS
If you like to bookmark sites that you access frequently so that you don't have to type in the
full site address, remember to bookmark the secure version of each site instead of the insecure
In Firefox, you can install the HTTPS Everywhere extension to turn on HTTPS automatically
whenever you visit a site that's known to offer HTTPS. It is available from
Risks when not using HTTPS
When you don't use HTTPS, a network operator such as your ISP or a national firewall operator,
can record everything you do including the contents of the specific pages that you access. They
can use this information to block particular pages or to create records that might be used
against you later on. They can also modify the contents of Web pages to delete certain
information or to add malicious software to spy on you or infect your computer. In many cases,
other users of the same network can also do these things even if they aren't officially the
network operator.
In 2010, some of these problems were dramatized by a program called Firesheep, which makes it
extremely easy for users on a network to take over other users' social networking site
accounts. Firesheep works because, at the time it was created, these social networking sites
were not commonly using HTTPS, or were using it in a limited way to protect only some portions
of their sites. This demonstration created a lot of attention in international media, and also led
more sites to require the use of HTTPS or to offer HTTPS access as an option. It also allowed
technically unskilled people to abuse others by breaking into their accounts.
In January 2011, during a period of political unrest in Tunisia, the Tunisian government began
tampering with users' connections to Facebook in a way that allowed the government to steal
users' passwords. This was done by modifying the Facebook login page and invisibly adding
software that sent a copy of the user's Facebook password to the authorities. Such
modifications are technically straightforward to perform and could be done by any network
operator at any time. As far as we know, Tunisian Facebook users who were using HTTPS were
totally protected from this attack.
Risks when using HTTPS
When it's available, using HTTPS is almost always safer than using HTTP. Even if something goes
wrong, it shouldn't make your communications any easier to spy on or filter. So it makes sense
to try to use HTTPS where you can (but be aware that, in principle, using encryption could be
restricted by law in some countries). However, there are some ways that HTTPS might not
provide complete protection.
Certificate warnings
Sometimes, when you try to access a web site over HTTPS, your Web browser will show you a
warning message describing a problem with the site's digital certificate. The certificate is used
to ensure the security of the connection. These warning messages exist to protect you against
attacks; please don't ignore them. If you ignore or bypass certificate warnings, you may still be
able to use a site but limit the ability of the HTTPS technology to protect your communications.
In that case, your access to the site could become no more secure than an ordinary HTTP
If you encounter a certificate warning, you should report it by e-mail to the Webmaster of the
site you were trying to access, to encourage the site to fix the problem.
If you're using an HTTPS site set up by an individual, such as some kinds of Web proxies, you
might receive an certificate error because the certificate is self-signed, meaning that there is
no basis given for your browser to determine whether or not the communication is being
intercepted. For some such sites, you might have no alternative but to accept the self-signed
certificate if you want to use the site. However, you could try to confirm via another channel,
like e-mail or instant messaging, that the certificate is the one you should expect, or see
whether it looks the same when using a different Internet connection from a different computer.
Mixed content
A single Web page is usually made up of many different elements, which can come from different
places and be transferred separately from one another. Sometimes a site will use HTTPS for
some of the elements of a Web page but use insecure HTTP for the others. For example, a site
might allow only HTTP for accessing certain images. As of February 2011, Wikipedia's secure site
has this problem; although the text of Wikipedia pages can be loaded using HTTPS, all of the
images are loaded using HTTP, and so particular images can be identified and blocked, or used to
determine which Wikipedia page is a user is reading.
Redirection to insecure HTTP version of a site
Some sites use HTTPS in a limited way and will force users back to using insecure HTTP access
even after the user initially used HTTPS access. For example, some sites use HTTPS for login
pages, where users enter their account information, but then HTTP for other pages after the
user has logged in. This kind of configuration leaves users vulnerable to surveillance. You should
be aware that, if you get sent back to an insecure page during the course of using a site, you no
longer have the protections of HTTPS.
Networks and firewalls blocking HTTPS
Because of the way HTTPS hinders monitoring and blocking, some networks will completely block
HTTPS access to particular Web sites, or even block the use of HTTPS altogether. In that case,
you may be limited to using insecure access to those sites while on those networks. You might
find that you're unable to access a site because of blocking of HTTPS. If you use HTTPS
Everywhere or certain similar software, you may not be able to use some sites at all because
this software does not permit an insecure connection.
If your network blocks HTTPS, you should assume that the network operator can see and record
all of your Web browsing activities on the network. In that case, you may want to explore other
circumvention techniques, particularly those that provide other forms of encryption, such as
VPNs and SSH proxies.
Using HTTPS from an insecure computer
HTTPS only protects the contents of your communications while they travel over the Internet. It
doesn't protect your computer or the contents of your screen or hard drive. If the computer you
use is shared or otherwise insecure, it could contain monitoring or spying software, or censorship
software that records or blocks sensitive keywords. In that case, the protection offered by
HTTPS could be less relevant, since monitoring and censorship could happen within your
computer itself, instead of at a network firewall.
Vulnerability of HTTPS certificate system
There are problems with the certificate authority system, also called public-key infrastructure
(PKI) used to authenticate HTTPS connections. This could mean that a sophisticated attacker
could trick your browser into not displaying a warning during an attack, if the attacker has the
right kind of resources. It has not yet been clearly documented that this is taking place
anywhere. This is not a reason to avoid using HTTPS, since even in the worst case, the HTTPS
connection would be no less secure than an HTTP connection.
7. Simple Tricks
8. Get Creative
9. Web Proxies
10. Psiphon
11. SabzProxy
There are a number of techniques to get past Internet filtering. If your aim is simply to reach
pages or services on the Internet that are blocked from your location, and you are not
concerned whether other people can detect and monitor your circumvention, these techniques
may be all you need:
using alternative domain names or URLs to reach blocked content
using third-party Web sites to reach blocked content
using e-mail gateways to retrieve blocked Web pages over e-mail.
HTTPS is the secure version of the HTTP protocol used to access Web sites.
In certain countries, and if the site you want to see has enabled HTTPS, just entering its address
(URL) beginning with https:// instead of http:// may allow you to access the site, even when the
http:// URL is blocked.
For instance has been blocked in Burma, whereas has
been accessible.
Before trying any other circumvention tool or technique, try adding an s after http in the URL of
your target site, if the http:// URL has been blocked. If this works, not only you will access the
target site, but the traffic between you and the site will also be encrypted.
For extra details on this technique, read the chapters "Confidentiality and HTTPS" and "HTTPS
One of the most common ways to censor a Web site is to block access to its domain name, for
example, "". However, sites are often accessible at other domain names, such as
"". If one domain name is blocked, try to find out if the content is available at
another domain.
You could also try to access special versions that some Web sites create for smartphones.
These are often the same URL with the addition of "m" or "mobile" at the beginning, for
example: (Gmail) or
There are a number of different ways you can reach the content on a Web page by going
through a third-party web site rather than directly to the source Web site.
Cached Pages
Many search engines keep copies of Web pages they have previously indexed, called cached
pages. When searching for a Web site, look for a small link labeled "cached" next to your search
results. Since you are retrieving a copy of the blocked page from the search engine's servers,
and not from the blocked Web site itself, you may be able to access the blocked content.
However, some countries have targeted caching services for blocking as well.
RSS Aggregators
RSS aggregators are Web sites that allow you to subscribe to and read RSS feeds, which are
streams of news or other information put out by sites you have chosen. (RSS stands for "Really
Simple Syndication"; for more on how to use it, see An RSS
aggregator connects to Web sites, downloads the feeds that you have selected, and displays
them. Since it is the aggregator connecting to the Web sites, and not you, you may be able to
access sites that would otherwise be blocked. This technique works only for Web sites that
publish RSS feeds of their content, of course, and therefore is most useful for blogs and news
sites. There are a lot of free, online RSS aggregators available. Some of the most popular ones
include Google Reader (, Bloglines ( or
Friendfeed (
Below is an example of Google Reader displaying the news:
There are many language translation services available on the Internet, often provided by search
engines. If you access a Web site through a translation service, the translation service is
accessing the blocked site, not you. This allows you to read the blocked content translated into a
number of different languages.
You can use the translation service to bypass blocking, even if you don't actually need to
translate the text. You do this by choosing translation from a language that does not appear on
the original Web site back to the original language. For example, to use a translation service to
view an English-language Web site, choose translation from Chinese to English. The translation
service translates only the Chinese sections (there are none), and leaves the English sections
(which is the whole Web page) untranslated.
Popular translation services include and
The example below illustrates the three steps necessary to view a page in Babelfish. First, enter
the URL of the Web site you wish to visit:
Next, choose the language you wish to read the Web site in. In this example, we tell Babelfish to
translate from Korean to English. Since there is no Korean text, the page will remain
When you have chosen the language, click "Translate" and the page displays.
Of course this requires that the translator site itself is accessible, which is not always the case
because some blocking authorities are aware of the potential use of translators for
For instance is not accessible in Saudi Arabia, according to
Low-Bandwidth Filters
Low-bandwidth filters are Web services designed to make browsing the Web easier in places
where connection speeds are slow. They remove or reduce images, remove advertisements, and
otherwise compress the Web site to make it use less data, so that it downloads faster.
But, as with translation and aggregation services, you can also use low-bandwidth filters to
bypass simple Web site blocking by fetching Web sites from their servers rather than from your
computer. One useful low-bandwidth filter is at
Web archive
The cache (the Wayback Engine - allows users
to see archived versions of web pages of the past. Millions of Web sites and their associated
data (images, source code, documents, etc.) are saved in a gigantic database.
Not all Web sites are available, however, because many Web site owners choose to exclude their
sites; also snapshots usually take at a long time to be added.
E-mail and Web mail services can be used to share documents with groups of friends or
colleagues, and even to browse the Web.
Accessing Web pages through e-mail
Similar to low-bandwidth filters, there are services intended for people with slow or unreliable
Internet connections that let you request a Web page via e-mail. The service sends a reply email that includes the requested Web page either in the body of the message or as an
attachment. These services can be quite cumbersome to use, since they require you to send a
separate request for one or more Web pages, and then wait for the reply, but, in certain
situations, they can be very effective at reaching blocked Web pages, especially if you use them
from a secure Web mail service.
One such service is To use it, send an e-mail message to [email protected]
with the Web address (URL) of the Web page you want in the subject line. You can also perform
simple Web searches by typing searches into the subject line. For example you can search for
censorship circumvention tools by typing "search censorship circumvention tools" in the subject
line of an e-mail message and sending it to [email protected]
Another service of the same kind is EmailTheWeb,, that allows you
to e-mail any Web page to anyone, including to yourself. To send the Web page by e-mail you will
need to register on the site or to use your Gmail account. The free service allows you to send up
to 25 pages per day.
You can find more information and support on this topic on the ACCMAIL mailing list. To
subscribe, send an e-mail with "SUBSCRIBE ACCMAIL" in the body to [email protected]
RSS to e-mail
Some platforms offer a similar Web to e-mail service, but with a focus on RSS feeds rather
simple Web pages; they include:
(Feed over Email) is another interesting project of the same kind, created by Sho Sing Ho from
the Broadcasting Board of Governors. At the time of writing this, FoE is still under development.
The progress of FoE can be followed here:
If you are interested in accessing filtered news in Persian from inside Iran, Sabznameh is an
option that you should consider. Sabznameh is a robust and scalable "feeds over e-mail"
newsletter platform that allows independent news consumers to access censored and blocked
content via e-mail.
The simplest way to access Sabznameh is to send a blank e-mail (with empty subject and body)
to [email protected] This way you can register even if you can't access the Web site You will receive a reply by e-mail that will guide you through the steps to
register to one or more of the publications available.
Using Web mail to share documents
If you are trying to share documents online, but want to control who can see them, you can
keep them in a private space where they are visible only to those with the correct password. A
simple way to share documents among a small group of friends or colleagues is to use a single
Web mail account with an online e-mail provider, such as Gmail (, and to
share the user name and password with those who need to access the documents. Since most
Web mail providers are free, it is easy to switch to a new account at intervals, making it harder
for anyone outside the group to keep track of what you are doing. A list of free online e-mail
providers is located at
These simple techniques are quick and easy to use; you can try them with minimal effort. Many
of them will work at least some of the time in many situations. However, they are also easy to
detect and block. Since most of them do not encrypt or otherwise hide your communications,
they are also vulnerable to keyword-based blocking and monitoring.
If your Internet Service Provider (ISP) censors access to certain Web sites or services, you can
use the tools described in the other chapters of this book, or you can think about creative ways
to access unfettered information. Here are some examples.
Sometimes filtering regulations are not applied uniformly and consistently by all ISPs. Big
providers with large numbers of subscribers, as well as state-owned telecommunications
companies, may be subject to more scrutiny and more extensive law enforcement than small
Internet start-ups. In 2002 the German government passed a law regulating the Internet that
was applicable to ISPs based in only one of its states. Users therefore were able to circumvent
these regulations by subscribing to a nationwide ISP with offices in other regions of the country.
Similarly, a German regulation imposed in 2010 that would affect only ISPs with over 10,000
subscribers (in order to prevent a leak of the blacklist) was easily overcome by subscribing to
small, local ISPs. During the 2011 Egyptian revolution, there has been speculation that Noor DSL
was the last ISP to comply with the Internet shutdown order because of its relatively small
market participation (8%) and the prominence of its customers, such as the Egyptian stock
exchange, the National Bank of Egypt and Coca-Cola.
Alternative ISPs can also be found abroad, and some companies even waive the subscription fee
for users who live in a country where there is severe political unrest. During the revolts of 2011
in Libya and Egypt, several citizens were able to publicize the political and social situations in
their respective countries by hooking up their dial-up modems to ISPs abroad, or by using
alternative communications methods, such as satellite, packet radio, and unfiltered connectivity
provided by multinational companies or embassies.
Mobile networks are increasingly popular means of disseminating and accessing uncensored
information, partly because of their high penetration rates in countries where the costs of
owning a computer or a private Internet connection are prohibitive. Because many mobile
carriers are not ISPs, their networks may not be affected by regulations in exactly the same
way. However, these networks are usually easier to monitor and are frequently subject to
extensive surveillance.
Activists in several countries have used their phones and free, open-source software such as
FrontlineSMS ( to manage short message service (SMS) campaigns
and bridge SMS technology with microblogging services, such as Twitter. A computer running
FrontlineSMS and connected to the Internet can serve as a platform for others to post
information to the Internet through their cell (mobile) phones.
Mobile networks can also be used with alternative devices. Amazon's Kindle 3G e-book reader,
for example, comes with free international mobile roaming, which allows free access to Wikipedia
through the mobile network in more than 100 countries.
Sometimes access to the Internet is completely restricted, and activists are forced to use
alternative means to distribute and access uncensored information. In 1989, well before the
Internet was widespread, some students from the University of Michigan purchased a fax
machine to send daily summaries of international media to universities, government entities,
hospitals, and major businesses in China to provide an alternative to the government's reports
about the events at Tiananmen Square.
If your access to the Internet is restricted, consider the possibility of conducting peer-to-peer
exchanges through alternative means. IrDA (Infrared) and Bluetooth are available in most modern
mobile phones and can be used to transfer data over short distances. Other projects, such as
"The Pirate Box" (, use Wi-Fi and free, open source software
to create mobile file-sharing devices. In countries with low Internet penetration, such as Cuba,
USB flash drives have garnered widespread use by people who want to distribute uncensored
information. Other technologies that were used by activists during the 2011 political unrest in
Libya and Egypt include fax, speak2tweet (a platform launched by Google and Twitter that
enables landline users to tweet via voicemail) and SMS.
Sometimes a censor's filtering and monitoring techniques are only applied to current standard
Internet protocols and services, so consider using very old or very recent technology that may
not be blocked or monitored. Before the advent of instant messaging (IM) software (Windows
Live Messenger, AIM, etc.) group communication was performed using Internet Relay Chat (IRC), a
protocol that allows real-time Internet text messaging. Although less popular than its successors,
IRC still exists and is still widely used by a big community of Internet users. A bulletin board
system (BBS) is a computer running software that allows users to connect, upload and download
software as well as other data, read news, and exchange messages with other users. Originally
users would call a telephone number using their modems to access these systems, but by the
early 1990s some bulletin board systems also allowed access over Internet interactive text
protocols, such as Telnet and, later, SSH.
In this regard, new technologies enjoy many of the the same benefits as old technologies, as they
are used by limited numbers of users and therefore are less subject to censorship. The new
Internet protocol IPv6, for example, is already deployed over some ISPs in some countries, and
usually it is not filtered.
Many Internet users whose connections are censored have started using Web services in ways
different than those for which they were initially designed. For example, users have employed
the chat capabilities of some video games to discuss sensitive matters that would otherwise be
detected in common chat rooms. Another technique is to share a single e-mail account and save
the conversation in the "Drafts" folder to avoid sending any e-mails over the Internet.
Online backup services such as and have been used by activists to
distribute and share documents, as well as other kinds of data.
Services that are intended for translation, caching, or formatting have been used as simple
proxies to bypass Internet censorship. Prominent examples are Google Translator, Google Cache,
and However, there are many creative applications, such as
(takes screenshots of Web sites), (creates a PDF from a Web site), (creates a PNG image from a URL), and (creates easy-to-read
documents for e-book readers, such as Nook and Kindle).
If you have any kind of communication channel with a co-operative person or computer outside
of the censorship you're experiencing, you should be able to turn it into a means of
circumventing censorship. As mentioned above, people have already used video game chat to
bypass censorship because censors often didn't think to monitor or censor it or to block access
to popular video games. In games that allow players to create sophisticated in-world objects,
people have discussed the idea of creating in-world computers, TV screens, or other devices that
players could use to get uncensored access to blocked resources.
People have also suggested the idea of disguising information within social networking site
profiles. For example, one person could put the address of a Web site he wanted to access in a
disguised form inside his social networking site profile. A friend with uncensored access would
then create an image of the contents of that site as a graphics file and post that in a different
profile. This process could be automated by software so that it happens quickly and
automatically, rather than requiring human beings to do the work.
With the help of computer programming, even a channel that simply allows a small amount of
numeric or textual information to flow back and forth can be converted into a communications
channel for a Web proxy. (When a channel hides the existence of some kind of communications
entirely, it's called a covert channel.) For example, programmers have created IP-over-DNS or
HTTP-over-DNS proxy applications to circumvent firewalls using the Domain Name System (DNS).
An example is the iodine software at You can also read
documentation for similar software at and With these applications, a request to access something is disguised as a
request to look up the addresses of a large number of unrelated sites. The content of the
information requested is then disguised as the content of the replies to these requests. Many
firewalls are not configured to block this kind of communication, because the DNS system was
never intended to be used to carry end-user communications rather than basic directory
information about sites' locations.
Many clever applications that use covert channels for circumvention are possible, and this is an
area of ongoing research and discussion. To be useful, these require a dedicated server
elsewhere, and the software at both ends must be set up by technically sophisticated users.
A proxy allows you to retrieve a Web site or other Internet resource even when direct access to
that resource is blocked from your location. There are many different kinds of proxies, including:
Web proxies, which only require that you know the proxy Web site's address. A Web proxy
URL may look like
HTTP proxies, which require that you or a piece of software modify your browser settings.
HTTP proxies only work for Web content. You may get the information about a HTTP
proxy in the format "" or "".
SOCKS proxies, which also require that you or a piece of software modify your browser
settings. SOCKS proxies work for many different Internet applications, including e-mail and
instant messaging tools. The SOCKS proxy information looks just like HTTP proxy
A Web proxy is like a browser embedded inside a Web page, and typically features a small form
where you can submit the URL of the Web site that you want to access. The proxy then shows
you the page, without requiring that you connect to it directly.
When using a Web proxy, you do not have to install software or change settings on your
computer, which means that you can use a Web proxy from any computer, including those at
Internet cafés. Simply enter the URL of the Web proxy into your browser, enter the destination
URL you wish to visit into the Web proxy, and press Enter or click the submit button.
Once you are viewing a page through a Web proxy, you should be able to use your browser's
forward and back buttons, click on links and submit forms without losing your proxied connection
to the filtered site. This is because your proxy has rewritten all of the links on that page so that
they now tell your browser to request the destination resources through the proxy. Given the
complexity of today's Web sites, however, this can be a difficult task. As a result, you might find
that some pages, links or forms "break out" of the proxied connection. Typically, when this
happens, the Web proxy's URL form will disappear from your browser window.
You can find Web proxy URLs at sites such as, by signing up for a mailing
list such as the one at, by following a country-specific
twitter feed, or simply by searching for "free Web proxy" in a search engine. lists
thousands of free Web proxies:
Examples of Web proxy platforms include CGIProxy, PHProxy, Zelune, Glype, Psiphon, and Picidae.
As mentioned above, these are not tools that you install on your own computer. They are
server software that someone else must install on a computer that is connected to the Internet
in a location that is not subject to filtering. All of these platforms provide the same basic
functionality, but they look different and may have different strengths and weaknesses. Some
are better at certain things, such as streaming videos or displaying complex Web sites
Some Web proxies are private. These are usually accessible only to a small group of users known
to the individual running the proxy or to customers who pay for the service. Private Web proxies
have certain advantages. Specifically, they may be:
more likely to remain undiscovered and therefore accessible
less congested and therefore faster
more trustworthy, assuming they are encrypted (see below) and run by someone you
Access may be restricted by requiring users to log in with a username and password or simply
by preventing the proxy URL from appearing in public directories such as those described above.
Web proxies are easy to use, but they have major disadvantages relative to other circumvention
tools. As a result, people often use them as a temporary way to obtain and learn how to use
more advanced tools, which must often be downloaded from Web sites that are themselves
filtered. Similarly, access to a Web proxy can be useful when attempting to fix or replace
another tool that has stopped working.
Web proxies only work for Web traffic, so they can not be used for other Internet services such
as e-mail or instant messaging. Many are also incompatible with complex Web sites like
Facebook, streaming multimedia content on sites such as YouTube, and encrypted sites that are
accessed through HTTPS. This latter restriction means that many Web proxies will be unable to
help you reach filtered sites that require a login, such as Web-based e-mail services. Worse yet,
some Web proxies cannot themselves be accessed through HTTPS. If you use such a proxy to log
in to a destination site that is normally secure, you may be putting your sensitive information,
including your password, at risk.
Security issues like this are discussed in more detail below.
With the notable exception of the HTTPS concerns described above, most Web proxy
compatibility issues can be resolved by using the "mobile" or "basic HTML" version of the
destination Web site, provided one is available. Unfortunately, relatively few sites offer this kind
of simplified interface, and even fewer do so in a way that exposes all of the site's functionality.
If a Web site does provide a mobile version, its URL will frequently begin with an "m" instead of
"www." Examples include,, and You can sometimes find a link for the mobile or basic HTML version of a
Web site among the small links toward the bottom of the site's main page.
You should be aware of some of the risks associated with the use of Web proxies, particularly
those operated by individuals or organizations you do not know. If you use a Web proxy simply
to read a public Web site such as, your only real concerns are that:
someone might learn that you are viewing a censored news source
someone might learn which proxy you rely on to do so.
Furthermore, if your Web proxy is working properly, and if you access it through HTTPS, the
former information should only be available to the administrator of the proxy itself. However, if
you rely on an insecure HTTP connection or if your proxy malfunctions (or is poorly designed) this
information will be revealed to anyone who might be monitoring your Internet connection. In fact,
unencrypted Web proxies do not work at all in some countries, because they cannot circumvent
filters that rely on keywords, rather than URLs or IP addresses, to block content.
For some users, the risks above are not a major concern. However, they may become quite
serious if you intend to use a Web proxy to access certain types of online resources, such as:
sites that require you to log in with a password
sites through which you intend to access sensitive information
sites through which you intend to create or share content
online commerce or Web banking sites
sites that support HTTPS encryption themselves.
In such cases, you should avoid using insecure or untrusted Web proxies. In fact, you might want
to avoid using a Web proxy altogether. While there is no guarantee that a more "advanced" tool
will be more secure, the challenges that installable circumvention software must address in order
to keep your traffic private are generally less complex than those faced by Web proxy software.
Obfuscation is not encryption
Some Web proxies, most notably those that lack support for HTTPS, use simple encoding
schemes to circumvent poorly-configured domain name and keyword filters. One such scheme,
called ROT-13, replaces each character with whatever lies 13 places ahead of it in the standard
Latin alphabet. (See to try it out for yourself.) Using ROT-13, the URL becomes uggc://jjj.oop.pb.hx, which would make it unrecognizable to a very
basic keyword filter. Proxy designers have found this trick useful even in countries where
keyword filtering is not present, because Web proxies often include the target URL inside the
actual URL that your browser sends to the proxy every time you click on a link or submit a new
address. In other words, when using a proxy, your browser might request instead of just, but a
domain name filter written to catch the latter would catch the former just as readily., on the other hand, might slip through the
filter. Unfortunately, character encoding schemes are not very reliable. After all, there is nothing
to prevent a censor from adding "jjj.oop.pb.hx" to the blacklist along with "" (Or,
better yet, she could add "uggc://" to the list, which would block all use of the proxy.)
The important thing to remember about character encoding is that it does not protect your
anonymity from third party observers, who can still track the list of sites that you visit. And,
even if it is applied to the full text of the pages you view and content you submit (rather than
just to URLs), it still can not provide confidentiality. If these things matter to you, restrict your
use of Web proxies to those that support HTTPS.
Don't forget, the proxy administrator can see everything.
The advice above emphasizes the importance of HTTPS, both on the censored target site and on
the proxy itself, when using a Web proxy to create or obtain sensitive information. However, it is
important to note that even when you access a secure site through a secure proxy, you are still
putting a great deal of faith in whoever administers your Web proxy, as that individual or
organization can read all of the traffic that you send or receive. This includes any passwords that
you might have to submit in order to access the destination Web site.
Even the more advanced circumvention tools, which tend to require that you install software on
your computer, must rely on some kind of intermediary proxy in order to circumvent Web
filters. However, all reputable tools of this kind are implemented in such a way as to protect the
content of HTTPS Web traffic even from the circumvention services themselves. Unfortunately,
this is not possible for Web proxies, which must rely more heavily on good old-fashioned trust.
And trust is a complicated function, that depends not only on a service administrator's
willingness to protect your interests, but also on her logging and record-keeping policies, her
technical competency, and the legal and regulatory environment in which she operates.
Tools designed to circumvent filtering do not necessarily provide anonymity, even those that
might include words like "anonymizer" in their names! In general, anonymity is a much more
elusive security property than basic confidentiality (preventing eavesdroppers from viewing the
information that you exchange with a Web site). And, as discussed above, even to ensure basic
confidentiality through a Web proxy requires, at the very least, that you:
use an HTTPS Web proxy
connect through that proxy to an HTTPS destination Web site
trust the proxy administrator's intentions, policies, software and technical competence
heed any browser warnings, as discussed in the HTTPS chapter of this book.
All of these conditions are also prerequisites for any degree of anonymity. If a third party can
read the content of your traffic, he can easily connect your IP address with the list of specific
Web sites that you visit. This is true even if, for example, you log in to those sites or post
messages on them using a pseudonym. (Of course, the opposite is true, as well. Even a perfectly
secure proxy cannot protect your identity if you sign your name to a public post on the
destination Web site!)
Advertising, viruses and malware
Some of the people who set up Web proxies do it to make money. They may do this simply and
openly by selling advertisements on each proxied page, as in the example below.
Or, a malicious proxy administrator might try to infect his users' computers with malware. These
so-called "drive-by-downloads" can hijack your computer for spamming or other commercial or
even illegal purposes.
The most important thing you can do to protect yourself against viruses and other malware is to
keep all of your software – especially your operating system and your anti-virus scanner –
updated. You can also block ads by using the AdBlockPlus extension (
and some malicious content by using the NoScript extension ( Both of these
extensions are for the Firefox Web browser. You can find more information on avoiding the risks
described above on the StopBadware Web site (
Cookies and scripts
There are also risks associated with the use of cookies and embedded scripts. Many Web
proxies can be configured to remove cookies and scripts, but many sites (for example, social
networking sites like Facebook and media streaming sites like YouTube) require them to work
properly. Web sites and advertisers can use these mechanisms to track you, even when you use
proxies, and to produce evidence that, for example, the person who did one thing openly is the
same person who did another thing anonymously. Some cookies may be saved on your computer
even after you restart it, so it might be a good idea to allow only selective use of cookies. In
Firefox, for example, you can instruct the browser to accept cookies only "Until I close Firefox".
(Similarly, you can instruct your browser to erase your browsing history when you close it.)
Generally speaking, however, Web proxies are extremely limited in their ability to protect your
identity from the Web sites that you access through them. If this is your goal, then you will have
to be very careful how you configure your browser and proxy settings, and you might want to
use a more advanced circumvention tool.
Helping others
If you are in a country with unrestricted Internet access and you are willing to help others get
around censorship, you can install a Web proxy script on your own Web site (or even on your
home computer), as discussed in the Helping Others section of this book.
Psiphon is an open-source Web proxy platform that has changed quite a bit over the past few
years. It differs from other proxy software (such as CGIProxy and Glype) in various ways,
depending on how it is configured on the server. In general, Psiphon:
is accessible through HTTPS
supports access to HTTPS destination sites
offers improved (though far from perfect) compatibility with a few complex Web sites,
including YouTube
may or may not require you to log in with a username and password
allows you to register an e-mail address to receive new proxy URLs from the
administrator in the event that your proxy is blocked
allows you to invite others to use your proxy (assuming it is configured to require a
The current version of the Psiphon server software runs only on Linux, and is much more
difficult to install and administer than most other proxies. It is designed primarily to facilitate the
operation of a large scale, blocking-resistant circumvention service for those who lack the ability
to install and use more advanced tools.
Psiphon 1, the original version of the Web proxy platform, was designed to run on Windows, and
allowed a non-expert computer user in a country that does not filter the Internet to provide
basic circumvention services to specific individuals from countries that do. It was easy to install,
easy to use and featured partial support for HTTPS, which made it more secure than many of
the alternatives. It also required users to log in, which helped prevent congestion and reduced
the likelihood that these small Web proxies, called nodes, would be targeted for blocking. Psiphon
1 is no longer maintained or supported by the organization that developed it.
Psiphon 2 was completely rewritten, with an eye toward performance, security, compatibility and
scalability in the context of a centralized service model. These goals have been met with varying
degrees of success. Initially, a Psiphon 2 user was required to log in to a particular private node
with a username and password. Psiphon, Inc. gave a few early users from each region additional
privileges that allowed them to invite others to access their proxies. Early Psiphon 2 proxies also
required users to ignore "invalid certificate" browser warnings because, while they were
accessible through HTTPS, their administrators were unable or unwilling to purchase signed SSL
certificates. All Psiphon private nodes deployed by the company itself now have signed
certificates and should not trigger browser warnings. Obviously, this might not hold true for
third-party installations of the Psiphon software. Finally, all Psiphon users now earn the right to
send a limited number of invitations.
Psiphon 2 open nodes, which were implemented somewhat later, can be used without logging in.
An open node automatically loads a particular homepage, and presents itself in a particular
language, but can then be used to browse elsewhere while evading online censorship. Open nodes
include a link through which a user can create an account and, optionally, register an e-mail
address. Doing so allows the proxy administrators to send a new URL to users whose nodes are
blocked from within their country. In general, open nodes are expected to be blocked and
replaced much more quickly than private nodes. As with new private nodes, all Psiphon open
nodes are secured using HTTPS, and those operated by Psiphon, Inc. identify themselves using
valid, signed certificates.
To limit and monitor the blocking of its proxies, Psiphon, Inc. has no centralized way to distribute
open nodes (which it sometimes refers to as right2know nodes). One English language open node,
dedicated to the Sesawe circumvention support forum, is available at Other open nodes are distributed privately (through mailing lists,
twitter feeds, radio broadcasts, etc.) by the various content producers that make up Psiphon's
client base.
Psiphon private nodes work differently. Even if it were possible to print an invitation link in this
book, it would be ill-advised, as the whole point of maintaining a private node is to limit its
growth and preserve some resemblance to a social network of trust among its members. After
all, a single invitation sent to a single 'informer' could be enough to get a node's IP address added
to a national blacklist. Worse yet, if that invitation were accepted, the informant would also
receive any replacement proxy URLs sent out by the system's administrators. If you do receive
an invitation, it will include a link similar to the following,
p=A9EE04A3, which will allow you to create an account and register an e-mail address. To do so,
follow the instructions under "Create an account", below. After creating your account, you no
longer need to use the invitation link. Instead, you will log in through a somewhat easier-toremember URL such as
The first time you connect to an open Psiphon proxy, you will see the "Psiphon Terms of Use and
Privacy Policy." Please read the terms carefully, as they contain important security advice as
well as information about how the proxy administrator claims to handle your data. In order to
use the proxy, you must click Agree.
After you accept the Terms of Use, Psiphon will load the default home page associated with that
node, as shown below. You can follow the links displayed on this page, which will automatically
request content through the proxy, or you can visit other Web sites using the blue URL bar
(called the Bluebar in Psiphon lingo) at the top of your browser window.
As long as you remember or bookmark the URL of an unblocked open node, you can use it to
access filtered Web sites. Creating an account allows you to modify certain preferences, including
the proxy's language and default home page. It also allows you to register an e-mail address so
that the node's administrator can e-mail you a new proxy URL if this one gets blocked. To do so,
click on the "Create account" link in the Bluebar.
If you receive an invitation to a Psiphon private node, the steps require to create your account
are identical to those described below.
When filling out the registration form, you might want to choose a username that is not
connected to your real identity through e-mail services, social networking sites, or other such
platforms. The same applies to your e-mail address, if you choose to register one. Most other
users of your proxy are prevented from seeing your username or your e-mail address, but both
items are stored in a database somewhere and are visible to Psiphon administrators. If you
choose to register an e-mail address, it is recommended that you select one that allows you to
access your e-mail through an HTTPS connection. Free e-mail providers that support HTTPS
include,, and To
prevent the automated registration of Psiphon accounts, you must read the number displayed on
the Security code image and enter it in the last field. When you are done, click "Create account".
You should see a message confirming the successful creation of your account. From now on
please use the URL displayed on this page to log in to your Psiphon node. Note that it includes an
HTTPS prefix and a short suffix ("/001" in the image above). You might want to print out this
welcome page or bookmark the linked URL (but be careful not to bookmark the welcome page
itself, by accident). Or course, you will also need the username and password that you chose in
the steps above.
This welcome page might also provide some advice, as shown above, about "invalid security
certificate" warnings and the need to accept them in order to use Psiphon. In fact, these
instructions are outdated, and you should no longer follow them. If, when connecting to a Psiphon
proxy, you see warnings such as those displayed below, you should pay attention to them. If that
happens, you might want to close your browser and contact [email protected] or
[email protected] for additional advice.
If you use an account to log in to your Psiphon proxy, you will eventually gain the ability to invite
others. In order to help prevent blocking, you will collect invite tokens slowly, and there is a limit
to the number that you can have at any one time. Obviously, if your proxy is an open node, you
can simply send the proxy URL to others. However, after a blocking event, if you receive a
follow-up "migration" message at your registered e-mail address, you might find that your
account has been moved to a private node. You should never share the URL of a private node,
except through Psiphon's built-in invitation mechanism.
Once you have collected one or more invitations, you will see an link on your Bluebar that says
something like Invite (1 remaining), as shown below.
There are two ways to invite others to use your Psiphon proxy:
The Send invitations method automatically sends invitation links to one or more recipients.
The invitation messages will come from Psiphon, not from your own account.
The Create invitations method generates one or more invitation links for you to distribute
through other channels.
If you click on the Bluebar link, you will be taken to the Send invitations screen. In order to
create an invitation link without e-mailing it, you must click on the Profile link first, then "Create
Send invitations
Click "Invite" on your Bluebar or Send invitations on the Profile screen. Enter an e-mail address
for each person to whom you want to send an invitation, one address per line, and then click
You will see a message telling you that one or more messages have been queued, which means
that Psiphon will e-mail out your invitation links within the next few minutes.
Remember that you should only invite people you know to private nodes.
Create invitations
Click "Create invitations" in the Profile screen. Select the number of invitation links to create and
click "Invite".
You may distribute these invitation links through whatever channels are available to you, but:
each invitation can be used only once
for private nodes, do not display the links publicly, to avoid exposing the proxy URL
for private nodes, you should only invite people you know.
Some Web sites that rely on embedded scripts and complex Web technology like Flash and AJAX
may not display properly through Psiphon. In order to improve Psiphon's compatibility with such
Web sites, the developers need to know which sites are problematic. If you find such a site, you
can report it easily by clicking the Broken Page link on the Bluebar. If you provide a brief
explanation of the problem in the Description field, it will allow the Psiphon development team to
reproduce the error and help them find a solution. When you have finished, click "Submit" and
your message will be sent to the developers.
SabzProxy ("green proxy" in Persian) is a free distributed Web proxy proposed by the team. It is based on the legacy code of PHProxy (which has not being maintained
since 2007). For additional detail about the Web proxies concept, please refer to the previous
The main improvement in SabzProxy, compared to PHProxy, is URL encoding. This makes
SabzProxy harder to detect (PHProxy has a predictive footprint that means it is now blocked in
several countries, including Iran). Only deep-packet inspection would allow SabzProxy servers to
be detected and blocked.
SabzProxy is localized in Persian but is fully functional in any language. Many people in various
countries have used it to set up their own public Web proxy.
Supported operating system
Web site
E-mail: [email protected]
SabzProxy is a distributed Web proxy. This means that there are neither central SabzProxy
instances, nor a commercial entity designed to create and diffuse them. Rather, it relies on its
community and users to create their own instances, and to share these to their network. You
can access instances through various forums, or networks, and when you have access you are
welcome to share it with your friends.
One dedicated instance is run by the Sesawe circumvention support forum, and it is available at (you can log in with the username flossmanuals, and
password flossmanuals).
If you own a Web hosting space and are interested in creating and sharing your SabzProxy
instance with your friends and family, please refer to the Installing SabzProxy chapter in the
Helping Others section of this book.
Here's an example that illustrates how SabzProxy works.
1. Enter the address of the SabzProxy instance you are using in your browser.
2. In the Web Address box on the SabzProxy page, enter the address of the censored Web
site you want to visit. For example, You can keep the
default options.
3. Click Go or Enter.
The Web site is displayed in the browser window.
You can see the SabzProxy green bar within the browser window, and the BBC Farsi Web site
below the bar.
To continue browsing, you can either:
Click any link from the current page. The Web proxy will automatically retrieve linked
Enter a new URL in the Address box at the top of the page.
Usually, you can keep the default options to browse. However you can choose between several
advanced options:
Include mini URL-form on every page / ‫ﻓﺮم آدرس‬
Check this option if you want to have a form on the proxified Web sites so that you can
enter new URLs without going back to the start page of SabzProxy. You may want to
deselect this option if you have a small screen, so you have more space for the target
Web page.
Remove client-side scripting (i.e., JavaScript) / ‫ﺣﺬ ف اﺳﻜﺮﻳ ﭙﺖ ﻫﺎ‬
Check this option if you want to remove dynamic technology scripting from Web pages.
Sometimes JavaScript can cause unwanted issues, as it is also used to display online ads
or even to track your identity. Browsing mobile/light versions of complex Web sites (like
Web mail services, or social networking platforms) is also an alternative to avoid Javascript
issues while using SabzProxy.
Allow cookies to be stored / ‫ﻗ ﺒﻮل ﮐﺮدن ﮐﻮﮐﯽ ﻫﺎ‬
Cookies are small pieces of text files which are often automatically stored by your Web
browser. They are required for Web sites which need authentication but can also be used
to track your identity. With this option turned on, every cookie is stored for a long time. If
you want to allow cookies for this session only, deselect this option and select "Store
cookies for this session only" (see below).
Show images on browsed pages / ‫ﻧﻤﺎﯾ ﺶ ﻋﮑﺴ ﻬﺎ‬
If you are on a slow Internet connection, you may want deselect this option so the pages
will be lighter, hence faster to load.
Show actual referring Web site / ‫ﻧﻤﺎﻳ ﺶ ﻣﺴ ﻴﺮﻫﺎ‬
By default, your browser sends every Web site the URL you are coming from, where you
have clicked on a link. These URLs are stored in the Web site log files and are analysed
automatically. For increased privacy, you can deselect this option.
Strip meta information tags from pages / ‫ﺣﺬ ف ﺗﮓ ﻫﺎي ﻣ ﺘﺎ‬
Meta tags are additional information stored in many Web sites to be used automatically by
computer programs. Such information may include the name of the author, description of
the site content or keywords for search engines. Filtering techniques could be run on these
tags. You may leave this option checked to avoid presenting this information to keyword
Strip page title / ‫ﺣﺬ ف ﻋ ﻨﻮان ﺻ ﻔ ﺤﺎت‬
With this option turned on, SabzProxy removes the page title of the Web site, which you
normally see in the title bar on top of your Web browser. This can be useful, for example
to hide the name of the Web site you are visiting if you don't want surrounding people to
see this when you minimize your browser.
Store cookies for this session only / ‫ﻛﻮﻛﻲ ﻫﺎ ﻣﻮﻗﺖ‬
Similar to the "Allow cookies to be stored" option; with this option turned on, cookies are
only stored until you close your SabzProxy session by exiting your Web browser.
12. Introduction to Firefox
13. Noscript and Adblock
14. HTTPS Everywhere
15. Proxy Settings and FoxyProxy
Our guess is that you wouldn't be reading this chapter unless you already knew what a Web
browser was. However, if you don't know, a browser is the software you use to visit and view
Web sites on the Internet.
In an earlier chapter, we explained that the Internet is a giant network of computers, all
connected to each other. Some of the computers are "Web servers" – computers that have
Web sites on them. If you want to visit these sites from your computer or a mobile device, you
need a way to surf around and display them. That's what a browser does.
One of the most popular browsers is Firefox, a free, open source Web browser created by the
Mozilla foundation in 2003. Firefox runs on all the major operating systems – Windows, MacOS
and Linux – and it has been translated into more than 75 languages. Best of all, It's completely
free of charge.
If you want to install Firefox you can find the installation files here:
When you visit this site you will be presented automatically with the correct installation file for
your operating system (Windows/Mac/Linux). For more information on how to install Firefox on
each of these operating systems, please see the FLOSS Manuals Firefox manual:
When you first download and install Firefox, it can handle basic browser tasks immediately. You
can also add extra capabilities or change the way Firefox behaves by installing add-ons, small
additions that extend Firefox's power. There are several kinds of add-ons:
extensions that provide additional functionality to the browser
themes that change Firefox's appearance
plugins that help Firefox handle things it normally can't process (for instance Flash movies,
Java applications, and so on).
The variety of add-ons available is enormous. You can add dictionaries for different languages,
track the weather in other countries, get suggestions for Web sites that are similar to the one
you are currently viewing, and much more.
Firefox keeps a list of current add-ons on its site (, or you can
browse them by category at
Before you install any add-on, keep in mind that it can read a lot of information from your
browser so it is very important to choose add-ons from trusted sources. Otherwise, an add-on
you install might share information about you without your knowing, keep a record or the sites
you have visited, or even harm your computer.
We recommend that you never install an add-on for Firefox unless it is available from the Firefox
add-on pages. You should also never install Firefox unless you get the installation files from a
trusted source. It is important to note that using Firefox on someone else's computer or in an
Internet café increases your potential vulnerability.
In the next three chapters, we will look at some add-ons that are particularly relevant for
dealing with Internet censorship.
While no tool can protect you completely against all threats to your online privacy and security,
the Firefox extensions described in this chapter can significantly reduce your exposure to the
most common ones, and increase your chances of remaining anonymous.
Adblock Plus ( scans Web pages for advertisements and other
content that may try to track you, and then blocks it. To keep current with the latest threats,
AdBlock Plus relies on blacklists maintained by volunteers.
Getting started with AdBlock Plus
Once you have Firefox installed:
1. Download the latest version of AdBlock Plus from or search for the plugin with Firefox's Add-ons
Manager ("Firefox" > "Add-ons").
2. Confirm that your want AdBlock Plus by clicking "Install Now".
3. After AdBlock Plus has been installed, Firefox will ask to restart.
Choosing a filter subscription
Adblock Plus by itself doesn't do anything. It can see each element that a Web site attempts to
load, but it doesn't know which ones should be blocked. This is what AdBlock's filters are for.
After restarting Firefox, you will be asked to choose a filter subscription (free).
Which filter subscription should you choose? Adblock Plus offers a few in its dropdown menu and
you may wish to learn about the strengths of each. A good filter to start protecting your privacy
is EasyList (also available at
As tempting as it may seem, don't add as many subscriptions as you can get, since some may
overlap, resulting in unexpected outcomes. EasyList (mainly targeted at English-language sites)
works well with other EasyList extensions (such as region-specific lists like RuAdList or thematic
lists like EasyPrivacy). But it collides with Fanboy's List (another list with main focus on Englishlanguage sites).
You can always change your filter subscriptions at any time within preferences (press
Ctrl+Shift+E). Once you've made your changes, click OK.
Creating personalized filters
AdBlock Plus also lets you create your own filters, if you are so inclined. To add a filter, start
with Adblock Plus preferences (Ctrl+Shift+E) and click on "Add Filter" at the bottom left corner of
the window. Personalized filters may not replace the benefits of well-maintained blacklists like
EasyList, but they're very useful for blocking specific content that isn't covered in the public lists.
For example, if you wanted to prevent interaction with Facebook from other Web sites, you
could add the following filter:
The first part (||facebook.*) will initially block everything coming from Facebook's domain. The
second part ($|~ is an exception that tells the filter to allow
Facebook requests only when you are in Facebook or if the Facebook requests come from (your own computer) in order to keep certain features of Facebook working.
A guide on how to create your own Adblock Plus filters can be found at
Enabling and disabling AdBlock Plus for specific elements or Web sites
You can see the elements identified by AdBlock Plus by clicking on the ABP icon in your
browser (usually next to the search bar) and selecting "Open blockable items", or by
pressing Ctrl+Shit+V. A window at the bottom of your browser will let you enable or disable each
element on a case-by-case basis. Alternatively, you can disable AdBlock Plus for a specific
domain or page by clicking on the ABP icon and ticking the option "Disable on [domain name]" or
"Disable on this page only".
The NoScript extension takes browser protection further by globally blocking all JavaScript, Java
and other executable content that could load from a Web site and run on your computer. To tell
NoScript to ignore specific sites, you need to add them to a whitelist. This may sound tedious,
but NoScript does a good job in protecting Internet users from several threats such as cross-site
scripting (when attackers place malicious code from one site in another site) and clickjacking
(when clicking on an innocuous object on a page reveals confidential information or allows the
attacker to take control of your computer). To get NoScript, visit or
The same method by which NoScript protects you can alter the appearance and functionality of
good Web pages, too. Luckily, you can adjust how NoScript treats individual pages or Web sites
manually – it is up to you to find the right balance between convenience and security.
Getting started with NoScript
1. Go to the NoScript download section at Click on the green
"INSTALL" button.
2. Confirm that you want NoScript by clicking "Install Now".
3. Restart your browser when asked.
NoScript notifications and adding Web sites to your whitelist
Once restarted, your browser will have a NoScript icon at the bottom right corner, where the
status bar is, indicating what level of permission the current Web site has to execute content on
your PC.
Full protection: scripts are blocked for the current site and its subframes. Even if some
of the script sources imported by the page are in your whitelist, code won't run (the
hosting documents are not enabled).
Very restricted: the main site is still forbidden, but some pieces (such as frames) are
allowed. In this case, some code may be running, but the page is unlikely to work correctly
because its main script source is still blocked.
Limited permissions: scripts are allowed for the main document, but other active
elements, or script sources imported by the page, are not allowed. This happens when
there are multiple frames on a page or script elements that link to code hosted on other
Mostly trusted: all the script sources for the page are allowed, but some embedded
content (such as frames) are blocked.
Selective protection: scripts are allowed for some URLs. All the others are marked as
All scripts are allowed for the current site.
Scripts are allowed globally, however content marked as untrusted will not be loaded.
To add a site that you trust to your whitelist, click on the NoScript icon and select:
"Allow [domain name]" to allow all scripts that are hosted under a specific domain name, or
"Allow all this page" to allow complete script execution - including third party scripts that
may be hosted elsewhere, but are imported by the main Web site.
(You can also use the "Temporarily allow" options to allow content loading only for the current
browsing session. This is useful for people who intend to visit a site just once, and who want to
keep their whitelist at a manageable size.)
Alternatively, you can add domain names directly to the whitelist by clicking on the NoScript
button, selecting Options and then clicking on the Whitelist tab.
Marking content as untrusted
If you want to permanently prevent scripts from loading on a particular Web site, you can mark
it as untrusted: just click the NoScript icon, open the "Untrusted" menu and select "Mark [domain
name] as Untrusted". NoScript will remember your choice, even if the "Allow Scripts Globally"
option is enabled.
HTTPS Everywhere is a Firefox add-on produced as a collaboration between The Tor Project
( and the Electronic Frontier Foundation ( It encrypts
your communications with a number of major Web sites, including Google, Wikipedia, and popular
social networking platforms such as Facebook and Twitter.
Many sites on the Web offer some support for encryption over HTTPS, but make it difficult to
use. For instance, they may connect you to HTTP by default, even when HTTPS is available. Or
they may fill encrypted pages with links that go back to the unencrypted site. This way, data
(such as usernames and passwords) sent to and received by these Web sites are transferred as
plain text and are easy to read by third parties.
The HTTPS Everywhere extension fixes these problems by rewriting all requests to these sites
to HTTPS. (Although the extension is called "HTTPS Everywhere", it only activates HTTPS on a
particular list of sites and can only use HTTPS on sites that have chosen to support it. It cannot
make your connection to a site secure if that site does not offer HTTPS as an option.)
Please note that some of those sites still include a lot of content, such as images or icons, from
third party domains that is not available over HTTPS. As always, if the browser's lock icon is
broken or carries an exclamation mark, you may remain vulnerable to some adversaries that
use active attacks or traffic analysis. However, the effort required to monitor your browsing
should still be usefully increased.
Some Web sites (such as Gmail) provide HTTPS support automatically, but using HTTPS
Everywhere will also protect you from SSL-stripping attacks, in which an attacker hides the
HTTPS version of the site from your computer if you initially try to access the HTTP version.
Additional information can be found at:
First, download the HTTPS Everywhere extension from the official Web site:
Select the newest release. In the example below, version 0.9.4 of HTTPS Everywhere was used.
(A newer version may be available now.)
Click on "Allow". You will then have to restart Firefox by clicking on the "Restart Now" button.
HTTPS Everywhere is now installed.
To access the HTTPS Everywhere settings panel in Firefox 4 (Linux), click on the Firefox menu at
the top left on your screen and then select Add-ons Manager. (Note that in different versions of
Firefox and different operating systems, the Add-ons Manager may be located in different places
in the interface.)
Click on the Options button.
A list of all supported Web sites where HTTPS redirection rules should be applied will be
displayed. If you have problems with a specific redirection rule, you can uncheck it here. In that
case, HTTPS Everywhere will no longer modify your connections to that specific site.
Once enabled and configured, HTTPS Everywhere is very easy and transparent to use. Type an
insecure HTTP URL (for example,
Press Enter. You will be automatically redirected to the secure HTTPS encrypted Web site (in this
example: No other action is needed.
If networks block HTTPS
Your network operator may decide to block the secure versions of Web sites in order to
increase its ability to spy on what you do. In such cases, HTTPS Everywhere could prevent you
from using these sites because it forces your browser to use only the secure version of these
sites, never the insecure version. (For example, we heard about an airport Wi-Fi network where
all HTTP connections were permitted, but not HTTPS connections. Perhaps the Wi-Fi operators
were interested in watching what users did. At that airport, users with HTTPS Everywhere were
not able to use certain Web sites unless they temporarily disabled HTTPS Everywhere.)
In this scenario, you might choose to use HTTPS Everywhere together with a circumvention
technology such as Tor or a VPN in order to bypass the network's blocking of secure access to
Web sites.
Adding support for additional sites in HTTPS Everywhere
You can add your own rules to the HTTPS Everywhere add-on for your favorite Web sites. You
can find out how to do that at: The benefit of
adding rules is that they teach HTTPS Everywhere how to ensure that your access to these sites
is secure. But remember: HTTPS Everywhere does not allow you to access sites securely unless
the site operators have already chosen to make their sites available through HTTPS. If a site
does not support HTTPS, there is no benefit to adding a ruleset for it.
If you are managing a Web site and have made an HTTPS version of the site available, a good
practice would be to submit your Web site to the official HTTPS Everywhere release.
A proxy server allows you to reach a Web site or other Internet location even when direct
access is blocked in your country or by your ISP. There are many different kinds of proxies,
Web proxies, which only require that you know the proxy Web site's address. A Web proxy
URL may look like
HTTP proxies, which require that you modify your Browser settings. HTTP proxies only
work for Web content. You may get the information about a HTTP proxy in the format
"" or "".
SOCKS proxies, which also require that you modify your Browser settings. SOCKS proxies
work for many different Internet applications, including e-mail and instant messaging tools.
The SOCKS proxy information looks just like HTTP proxy information.
You can use a Web proxy directly without any configuration by typing in the URL. The HTTP and
SOCKS proxies, however, have to be configured in your Web browser.
In Firefox 4 (Linux), you enter the configuration screen by clicking on the Firefox menu at the top
left on your screen and then selecting Options. In the pop-up window, select the icon labeled
Advanced and then choose the Network tab. You should see this window:
Select Settings, click on "Manual proxy configuration" and enter the information of the proxy
server you want to use. Please remember that HTTP proxies and SOCKS proxies work
differently and have to be entered in the corresponding fields. If there is a colon (:) in your proxy
information, that is the separator between the proxy address and the port number. Your screen
should look like this:
After you click OK, your configuration will be saved and your Web browser will automatically
connect through that proxy on all future connections. If you get an error message such as, "The
proxy server is refusing connections" or "Unable to find the proxy server", there is a problem
with your proxy configuration. In that case, repeat the steps above and select "No proxy" in the
last screen to deactivate the proxy.
FoxyProxy is a freeware add-on for the Firefox Web browser which makes it easy to manage
many different proxy servers and change between them. For details about FoxyProxy, visit
In Firefox 4 (Linux), click on the Firefox menu at the top left on your screen and then select Addons. In the pop-up window, type the name of the add-on you want to install (in this case
"FoxyProxy") in the search box on the top right and click Enter. In the search results, you will see
two different versions of FoxyProxy: Standard and Basic. For a full comparison of the two free
editions, visit, but the Basic edition is sufficient
for basic circumvention needs. After deciding which edition you want, click Install.
After installation, Firefox should restart and open the Help site of FoxyProxy. You should see the
FoxyProxy icon at the bottom right.
For FoxyProxy to do its job, it needs to know what proxy settings to use. Open the configuration
window by clicking the icon at the bottom right of the Firefox window. The configuration window
looks like this:
Click on "Add New Proxy". In the following window, enter the proxy details in a similar way to the
default Firefox proxy configuration:
Select "Manual Proxy Configuration", enter the host or IP address and the port of your proxy in
the appropriate fields. Check "SOCKS proxy?" if applicable, then click OK. You can add more
proxies by repeating the steps above.
You can switch among your proxies (or choose not to use a proxy) by right-clicking on the fox
icon on the bottom right of your Firefox window:
To select a proxy server, simply left-click on the proxy you want to use.
16. Introduction
17. Freegate
18. Simurgh
19. UltraSurf
20. VPN Services
21. VPN on Ubuntu
22. Hotspot Shield
23. Alkasir
24. Tor : The Onion Router
25. JonDo
26. Your-Freedom
The basic idea of circumventing Internet censorship is to route the requests over a third server
which is not blocked and is connected to the Internet through a non filtered connection. This
chapter explains some of the tools which make it possible to use such a server in order to
defeat Internet blocking, filtering, and monitoring. The choice of which tool might best accomplish
your objectives should be based on an initial assessment on the type of content you want to
access, your available resources, and the risks of doing so.
Tools to defeat Internet blocking, filtering and monitoring are designed to deal with different
obstacles and threats. They may facilitate:
Circumventing censorship: enabling you to read or author content, send or receive
information, or communicate with particular people, sites or services by bypassing
attempts to prevent you from doing so. Similar to the operation of the Google cache or an
RSS aggregator which can be used to access a blocked Web site indirectly.
Preventing eavesdropping: keeping communications private, so that nobody can see or
hear the content of what you're communicating (even if they might still be able to see with
whom you're communicating). Tools that try to circumvent censorship without also
preventing eavesdropping may remain vulnerable to censorship by keyword filters that
block all communications containing certain prohibited words. For example, various forms
of encryption, such as HTTPS or SSH, make the information unreadable to anyone other
than the sender and receiver. An eavesdropper will see which user is connecting to which
Web server, but from the content he can only see a string of characters that looks like
Remaining anonymous: the ability to communicate so that no one can connect you to
the information or people you are connecting with – neither the operator of your Internet
connection nor the sites or people with whom you're communicating. Many proxy servers
and proxy tools don't offer perfect, or any, anonymity: the proxy operator is able to
observe the traffic going into and out of the proxy and easily determine who is sending it,
when they're sending it, and how often they're sending it; a malicious observer on either
side of the connection is able to gather the same information. Tools like Tor are designed
to make it difficult for attackers to gather this kind of information about users by limiting
the amount of information any node in the network can have about the user's identity or
Concealing what you are doing: disguising the communications you send so that
someone spying on you will not be able to tell that you are trying to circumvent
censorship. For example, steganography, the hiding of text messages within an ordinary
image file, may conceal that you are using a circumvention tool at all. Using a network with
many kinds of users means that an adversary can not tell what you are doing because of
your choice of software. This is especially good when others are using the same system to
get to uncontroversial content.
Some tools protect your communications in only one of these ways. For example, many proxies
can circumvent censorship but don't prevent eavesdropping. It's important to understand that
you may need a combination of tools to achieve your goal.
Each kind of protection is relevant to different people in different situations. When you choose
tools that bypass Internet censorship, you should keep in mind what kind of protection you need
and whether the particular set of tools you're using can provide that sort of protection. For
example, what will happen if someone detects that you are attempting to circumvent a
censorship system? Is accessing your main concern, or do you need to remain anonymous while
doing so?
Sometimes, one tool can be used to defeat censorship and protect anonymity, but the steps for
each are different. For instance, Tor software is commonly used for both purposes, but Tor
users who are most concerned with one or the other will use Tor differently. For anonymity
reasons, it is important that you use the Web browser bundled with Tor, since it has been
modified to prevent leaking of your real identity.
Most circumvention tools can be detected with sufficient effort by network operators or
government agencies, since the traffic they generate may show distinctive patterns. This is
certainly true for circumvention methods that don't use encryption, but it can also be true for
methods that do. It's very difficult to keep secret the fact that you're using technology to
circumvent filtering, especially if you use a fairly popular technique or continue using the same
service or method for a long period of time. Also, there are ways to discover your behavior that
do not rely on technology: in-person observation, surveillance, or many other forms of traditional
human information-gathering.
We cannot provide specific advice on threat analysis or the choice of tools to meet the threats.
The risks are different in each situation and country, and change frequently. You should always
expect that those attempting to restrict communications or activities will continue to improve
their methods.
If you are doing something that may put you at risk in the location where you are, you should
make your own judgments about your security and (if possible) consult experts.
Most often, you will have to rely on a service provided by a stranger. Be aware that they
may have access to information about where you are coming from, the sites you are
visiting and even the passwords you enter on unencrypted Web sites. Even if you know
and trust the person running a single-hop proxy or VPN, they may be hacked or forced to
compromise your information.
Remember that the promises of anonymity and security made by different systems may
not be accurate. Look for independent confirmation. Open source tools can be evaluated
by tech-savvy friends. Security flaws in open source tools can be discovered and fixed by
volunteers. It is difficult to do the same with proprietary software.
Achieving anonymity or security may require you to be disciplined and carefully obey
certain security procedures and practices. Ignoring security procedures may dramatically
reduce the security protections you receive. It is dangerous to think that it is possible to
have a "one click solution" for anonymity or security. For instance, routing your traffic
through a proxy or through Tor is not enough. Be sure to use encryption, keep your
computer safe and avoid leaking your identity in the content you post.
Be aware that people (or governments) may set up honeypots – fake Web sites and
proxies that pretend to offer secure communication or censorship circumvention but
actually capture the communications from unwitting users.
Sometimes even "Policeware" may be installed on users' computers – either remotely or
directly – that acts like malware, monitoring all activities on the computer even when it is
not connected to the Internet and undermining most other preventive security measures.
Pay attention to non-technical threats. What happens if someone steals your computer or
mobile phone or that of your best friend? What if an Internet café staff member looks over
your shoulder or points a camera to your screen or keyboard? What happens if someone
sits down at a computer in a café somewhere where your friend has forgotten to log out
and sends you a message pretending to be from her? What if someone in your social
network is arrested and forced to give up passwords?
If there are laws or regulations that restrict or prohibit the materials you are accessing or
the activities you are undertaking, be aware of the possible consequences.
To learn more about digital security and privacy, read:
Freegate is a proxy tool for Windows users that was initially developed by DIT-INC to bypass
Internet censorship in China and Iran.
Supported operating system
English, Chinese, Persian, Spanish
Web site
You can download the software for free at
You will get a file with the extension .zip, which you have to extract first. Right-click on the
downloaded file and select "Extract All", then click on the button "Extract". The resulting file is
about 1.5 MB. The name of the executable file may look like a short series of letters and
numbers (e.g. "fg707p.exe").
When you run the application for the first time, you may see a Security Warning. You can accept
this Security Warning by unchecking the box "Always ask before opening this file" and clicking
Now the application should start and connect automatically to a server.
When the secure tunnel has started successfully, you will see the Freegate status Window and a
new instance of the Internet Explorer will open automatically with the URL
"" loaded, depending on your version and
language. This is the confirmation that you are using Freegate correctly through an encrypted
If all has gone well, you can start browsing normally using the automatically-opened Internet
Explorer window to get around Internet censorship.
If you want to use another application with Freegate (for example the Firefox Web browser or
the Pidgin instant messaging client), you will have to configure them to use Freegate as a proxy
server. The IP is, and the port is 8580.
Under the Settings tab in Freegate, you can choose your interface language from English,
Traditional Chinese, Simplified Chinese, Farsi and Spanish. Under Status, you can track your
upload/download traffic through the Freegate network. The Server tab allows you to pick from
several severs, one of which may be faster than your current connection.
Simurgh (which means "phoenix" in Persian) is a lightweight stand-alone proxy software and
service. This means that it can be run without any prior installation or administrator rights on
the computer. You can copy it to your USB flash drive and use it on a shared computer (in an
Internet café, for example).
Supported operating system
Web site
E-mail: [email protected]
To use the Simurgh service, download the tool for free from
It is available for any version of Microsoft Windows. The size of the file is less than 1MB, so it can
be downloaded even on a slow Internet connection in a reasonable time.
To start Simurgh, click on the file you have downloaded. By default, files downloaded with
Microsoft Internet Explorer are located on your Desktop and files downloaded with Mozilla Firefox
are located in "My Documents" and then "Downloads".
Note that when you run Simurgh for the first time, you may encounter a Windows Security Alert
which asks if you want to keep blocking Simurgh. Since Simurgh has to communicate with the
Internet in order to work it is very important that you select "Unblock" or "Allow Access"
(depending on your version of Microsoft Windows).
You may see this warning pop-up:
or this one:
After you have successfully started Simurgh, click on Start to create a secure connection.
When the Start button changed to a Stop button, Simurgh has successfully connected to its
Make sure you are connected to the Simurgh server
Now a new window of your Internet Explorer browser will open with a test page. If you see your
connection originating from another country, such as U.S.A., this confirms that Simurgh has
successfully changed the settings of your browser and you are automatically surfing over the
secure Simurgh connection.
You can also use the website to check where your connection appears
to be from. If the websites shows your location very far away (in another country such as the
USA), you are using the secure Simurgh connection.
In order to use another web browser like Mozilla Firefox, you need to configure it to use the
HTTP proxy "localhost" with the port 2048.
In Firefox, you can find the proxy settings via Tools > Options > Network > Settings.
In the "Connection settings" window choose "Manual proxy configuration" and enter "localhost"
(without the quotemarks) as the HTTP proxy and the port 2048, as shown in the screenshot
below. To accept the new settings, click OK.
UltraSurf, from developer UltraReach Internet Corp, is a proxy tool designed to help Chinese
Internet users to get around their censorship. It may work for users in other countries as well.
Supported operating system
Web site
You can download the free software (for Windows only), at or or (the latter page is in Chinese, but the
download is still easy to find and in English).
Once you have downloaded the file, named something like "" (depending on the version
number), extract it by right-clicking the file and selecting "Extract All". Double-click the new
"u1006" icon to start the application.
UltraSurf will automatically open Internet Explorer and display the UltraSurf search page You can now start browsing using the instance of
Internet Explorer that UltraSurf has launched.
If you want to use another application with UltraSurf (for example the Firefox Web browser or
the Pidgin instant messaging client), you need to configure them to use the UltraSurf client as a
proxy server: the IP is (your PC, also known as "localhost") and the port is 9666.
You can open the UltraSurf User Guide by clicking Help in the UltraSurf main window.
Info on Chinese UltraSurf (wujie):
Chinese user guide:
A VPN (virtual private network) encrypts and tunnels all Internet traffic between yourself and
another computer. This computer might belong to a commercial VPN service, your organization,
or a trusted contact.
Because VPN services tunnel all Internet traffic, they can be used for e-mail, instant messaging,
Voice over IP (VoIP) and any other Internet service in addition to Web browsing, making
everything that travels through the tunnel unreadable to anyone along the way.
If the tunnel ends outside the area where the Internet is being restricted, this can be an
effective method of circumvention, since the filtering entity/server sees only encrypted data,
and has no way of knowing what data is passing through the tunnel. It has the additional effect
of making all your different kinds of traffic look similar to an eavesdropper.
Since many international companies use VPN technology to allow employees who need access to
sensitive financial or other information to access the companies' computer systems from home
or other remote locations over the Internet, VPN technology is less likely to be blocked than the
technologies used only for circumvention purposes.
It is important to note that the data is only encrypted as far as the end of the tunnel, and then
travels unencrypted to its final destination. If, for example, you set up a tunnel to a commercial
VPN provider, and then request the Web page through the tunnel, the data
will be encrypted from your computer to the VPN provider's computer at the other end, but
from there it will be unencrypted to the servers run by the BBC, just like normal Internet traffic.
This means that the VPN provider, the BBC and anyone with control over a system between
these two servers, will, in theory, be able to see what data you sent or have requested.
VPN services might or might not require installation of client-side software (many rely on existing
VPN support in Windows, Mac OS or GNU/Linux and so need no extra client software).
Using a VPN service requires you to trust the owners of the service, but provides a simple and
convenient method of bypassing Internet filtering, for free or for a monthly fee generally
between 5 and 10 US dollars, depending on the service. Free services are often either adsupported, or limit the bandwidth and/or the maximum traffic allowed over a given period.
Popular free VPN services:
Hotspot Shield,
According to a 2010 report from the Berkman Center, Hotspot Shield is overwhelmingly the
most popular VPN service. For more details on how to get and use Hotspot Shield, read
the "Hotspot Shield" chapter of this manual.
Air VPN,
AirVPN offers free accounts without bandwidth or traffic restrictions and without ads for
activists by request.
Loki Network Project,
Examples of paid VPN services include Anonymizer, GhostSurf, XeroBank, HotSpotVPN, WiTopia,
VPN Swiss, Steganos, Hamachi LogMeIn, Relakks, Skydur, iPig,, FindNot, Dold,
UnblockVPN and SecureIX.
You can find a list of free and paid VPN providers, with their monthly fee and technical
characteristics at
There are a number of different standards for setting up VPN networks, including IPSec,
SSL/TLS and PPTP, that vary in terms of complexity, the level of security they provide, and
which operating systems they are available for. Naturally, there are also many different
implementations of each standard within software that have various other features.
While PPTP is known to use weaker encryption than either IPSec or SSL/TLS, it may still be
useful for bypassing Internet blocking, and the client software is conveniently built into
most versions of Microsoft Windows.
SSL/TLS-based VPN systems are relatively simple to configure, and provide a solid level of
IPSec runs at the Internet level, responsible for packet transfer in the Internet
architecture, while the others run at the Application level. This makes IPsec more flexible,
as it can be used for protecting all the higher level protocols, but also difficult to set up.
As an alternative to paying for commercial VPN services, users with contacts in unrestricted
locations may have these contacts download and install software that sets up a private VPN
service. This requires a much higher level of technical knowledge, but it will be free. Also the
private nature of such a setup means it is less likely to be blocked than a commercial service
that has been available for a long time. One of the most widely used free and open source
programs available for setting up this kind of private VPN is OpenVPN (, which
can be installed on Linux, MacOS, Windows and many other operating systems.
To understand how to set up an OpenVPN system, read the "Using OpenVPN" chapter in this
A VPN provides encrypted transfer of your data, so it is one of the safest ways to bypass
Internet censorship. Once configured, it is easy and transparent to use.
VPNs are best suited for technically capable users who require secure circumvention services for
more than just web traffic and who access the Internet from their own computer where they
can install additional software. VPNs are an excellent resource for users in censored locations
who do not have trusted contacts in non-filtered locations. VPN technology is a common
business application that is not likely to be blocked.
Some commercial VPNs (especially the free ones) are publicly known and may be filtered. They
normally cannot be used in public access locations where users cannot install software, such as
Internet cafés or libraries. Use of VPNs may require a higher level of technical expertise than
other circumvention methods.
A network operator can detect that a VPN is being used and determine who the VPN provider is.
The network operator should not be able to view the communications sent over the VPN unless
the VPN is set up incorrectly.
The VPN operator (much like a proxy operator) can see what you're doing unless you use some
additional encryption for your communications, like HTTPS for Web traffic; without additional
encryption, you have to trust the VPN or tunnel operator not to abuse this access.
If you use Ubuntu as your operating system, you can connect to a VPN by using the built-in
NetworkManager feature and the free OpenVPN client.
OpenVPN allows you to connect to VPN networks using a variety of authentication methods. For
our example, we'll learn how to connect to a VPN server using AirVPN, a free VPN service. The
configuration process for OpenVPN on Ubuntu is the same, regardless of which VPN service you
Installing OpenVPN for NetworkManager
NetworkManager, a network utility that will let you open or close your VPN connection, is
included with Ubuntu by default – you can find it in the notification area of your screen, right
next to your system clock.
Next, find an OpenVPN extension that will work with NetworkManager, from the Ubuntu
Software Center.
1. Open the Ubuntu Software Center from the Applications menu located at the top left of
your screen
2. The Ubuntu Software Center lets you search, install and remove software on your
computer. Click on the search box at the top right of the window.
3. In the search box, type in "network-manager-openvpn-gnome" (the extension for
NetworkManager that will enable OpenVPN). This package includes all the files you need to
establish a VPN connection successfully, including the OpenVPN client. Click on Install.
4. Ubuntu may ask you for additional permissions to install the program. If that is the case,
type in your password and click Authenticate. Once the package is installed, you can close
the Software Center window.
5. To check if the OpenVPN client is correctly installed, click on the NetworkManager (the icon
at the left of your system clock) and select VPN Connections > Configure VPN.
6. Click Add under the VPN tab.
7. If you see an OpenVPN option this means that you have installed the OpenVPN client in
Ubuntu correctly. Click on cancel and close the NetworkManager.
Registering an AirVPN account
AirVPN ( is a free service, but you will need to register at their Web site to
download the configuration files for your VPN connection.
1. Go to and register for a free account.
Make sure you pick a strong password, as this will also be the password for your VPN
access. (For tips on strong passwords, see the chapter on "Threats and Threat
Assessment" in this book.)
2. On AirVPN's site navigation menu, select More > Access with... > Linux/Ubuntu.
3. Click on "Access without our client". You will be prompted for the same username and
password you used when you registered.
4. Select the VPN Mode you would like to configure in NetworkManager (for our example we
used "Free - TCP - 53") and leave the rest of the options as they are. Make sure you have
checked the Terms of Service agreement at the bottom of the page, and then click
5. A pop-up window will let you know that the file is ready for downloading. This
contains the configuration files and credentials you need to connect to the VPN. Click OK.
Configuring AirVPN on NetworkManager
Now that you have your configuration files and credentials, you can configure NetworkManager
to connect to the AirVPN service.
1. Unzip the file you have downloaded to a folder on your hard drive (e.g.:
"/home/[yourusername]/.vpn"). You should now have four files. The file "air.ovpn" is the
configuration file that you need to import into NetworkManager.
2. To import the configuration file, open NetworkManager and go to VPN Connections >
Configure VPN.
3. Under the VPN tab, click Import.
4. Locate the file air.ovpn that you have just unzipped. Click Open.
5. A new window will open. Leave everything as it is and click Apply.
6. Congratulations! Your VPN connection is ready to be used and should appear on the list of
connections under the VPN tab. You can now close NetworkManager.
Using your new VPN connection
Now that you configured NetworkManager to connect to a VPN service using the OpenVPN client,
you can use your new VPN connection to circumvent Internet censorship. To get started, follow
these steps:
1. In the NetworkManager menu, select your new connection from VPN Connections.
2. Wait for the VPN connection to be established. When connected, a small padlock should
appear right next to your NetworkManager icon, indicating that you are now using a secure
connection. Move your cursor over the icon to confirm that the VPN connection is active.
3. You can also check the status of your connection by visiting
This free IP-checker should confirm that you are using a server.
4. To disconnect from your VPN, select VPN Connections > Disconnect VPN in the
NetworkManager menu. You are now using your normal (filtered) connection again.
Hotspot Shield is a free (but commercial) VPN solution available for Microsoft Windows and Mac
OS, which can be used to access the uncensored Internet through a secure tunnel (over your
normal, censored Internet connection).
Hotspot Shield encrypts all your communications, so your censor's surveillance software can't
see what sites you're accessing.
Supported operating
Web site
E-mail: [email protected]
Download the software from The file size is about 6MB, so on a
slow dial-up connection this can take up to 25 minutes or more. If the download is blocked from
where you are trying to access it, write to [email protected] and include at least one
of these words in the subject line of your e-mail: "hss", "sesawe", "hotspot" or "shield". You will
receive the installer as an e-mail attachment in your inbox.
Important: if you are using Firefox with the NoScript extension enabled, you may experience
some issues when trying to use Hotspot Shield. Make sure that all URLs that Hotspot Shield
connects to are whitelisted, or that you temporarily allow scripts globally while using this service.
Installing Hotspot Shield
1. After a successful download, locate the downloaded file on your computer and start the
installation by double clicking the icon
2. Windows may ask you for permission to install the software. Click Yes.
3. Select your preferred installation language from the dropdown menu.
4. After you select the language, you will see a welcome screen. Click Next.
5. Accept the license agreement by clicking on "I Agree".
6. You will see a window informing you about additional software which can be installed
optionally. Click Next.
7. On the next screen you can uncheck the option to install the optional Hotspot Shield
Community Toolbar. This feature is not needed to run Hotspot Shield.
8. Additional options will be presented at the next screen. All these features are optional, and
you don't need any of them enabled to run Hotspot Shield.
9. Select the location on your hard drive where you want Hotspot Shield to be installed. In
most cases you can leave the default values and proceed by clicking Install.
10. Windows may request additional permissions several times to install different components
of Hotspot Shield. You can safely proceed by clicking Install every time.
11. When the installation is completed, click Next.
12. Finally, you can launch Hotspot Shield immediately after installation and you can create an
icon for your desktop. Choose your preferences and click Finish.
Hotspot Shield is now installed on your computer.
Connecting to the Hotspot Shield service
1. Click on the Hotspot Shield Launch icon on your desktop or from the menu Programs >
Hotspot Shield.
2. Once you launch Hotspot Shield, a browser window will open with a status page showing
different stages of the connection attempt, such as "Authenticating" and "Assigning IP
3. Once connected, Hotspot Shield will redirect you to a welcome page. Click Start to begin
4. Please note that after you click Start, Hotspot Shield may redirect you to an
advertisement page such as the one displayed below. You can close this tab and start
surfing the Web as usual. You can check that you are connected to the Hotspot Shield
service by looking at the green Hotspot Shield icon in your system tray (next to the clock).
5. To check your connection status, simply right click on the Hotspot Shield system tray icon
and select Properties.
Disconnecting from the Hotspot Shield service
1. To disconnect from the Hotspot Shield service right click on the system tray icon (see
image above) and select Disconnect/OFF.
2. Hotspot Shield will ask you to confirm this action. Click Disconnect.
3. A status window will appear confirming you are now disconnected and surfing on your
normal (filtered) connection. Click on the "CONNECT" button to resume circumvention.
Alkasir is an innovative server/client tool facilitating the tracking, analysis, and circumvention of
Web site censorship (filtering). Alkasir is mainly used in the Middle East region but can be used
It utilizes a dedicated client software and is powered by proxy servers. Its innovative feature is
to keep the list of blocked sites up-to-date by getting semi-automatic updates, and allows
reporting of newly blocked sites through its globally-distributed user community.
Supported operating system
English and Arabic
Web site
Alkasir has implemented two innovative and complementary new features. It is designed as a
Web browser (based on Mozilla Firefox) with an embedded pre-configured HTTP proxy, and a selflearning blocked URLs database.
Bypassing Internet censorship
The innovation is that Alkasir only relies on its blocked URLs database and built-in proxy to
reach blocked URLs. Non-blocked URLs are accessed directly, without proxy requests. Using
HTTP proxy only when it is really needed optimizes bandwidth usage and allows non-blocked Web
pages to be accessed more quickly (since directly-accessed Web pages load quicker).
Keeping the blocked URLs database up-to-date
Any time a user suspects that a URL is blocked, he can report it via the software interface.
Alkasir checks the report thoroughly, then asks that country's moderator (a human person) to
approve that addition to the database (to keep the database relevant and to prevent
undesirable content, such as porn, from entering it).
A single "blocked content unit" (a Web site that is blocked in a certain country) is often
dependent on more than one URL. When Alkasir detects a blocked URL in a certain country, it
checks all the URLs referenced on that page to determine whether any of them are also
blocked. Thus, Alkasir builds its blocked content database through a simple, primitive, one-level
spidering methodology.
Finally, if an Alkasir user fails to load an URL with a direct request (i.e. not through the proxy),
the client notes this and automatically checks to see whether it is a new (not yet in the
database) blocked URL or not, and if it is, adds it automatically.
The database is available at the following address:
To summarise, Alkasir's blocked URLs database is continuously fed by all Alkasir users (using
human submissions or automatic reports) and the Alkasir browser relies on this database to
optimize the global tool's reactivity by redirecting only blocked URLs requests through the proxy.
You can download Alkasir directly from the website or receive it by e-mail.
Download Alkasir via the website
You can download Alkasir from the official website,
Depending on the operating system and programs you have, you will choose one of the following
If you have Windows Vista or Windows 7 and have Mozilla Firefox installed, you only need
the "Alkasir Installation package" (which requires installation, size: 3 MB).
If this is not the case, you need to download the "Alkasir Complete Installation package"
(which also requires installation, size: 41.04 MB)
If you are not able or do not want to install Alkasir permanently on the computer you are using
(e.g. a shared computer in an Internet café or library), you can download any of the two USB
versions of Alkasir:
Alkasir USB package without Mozilla (does not need installation – portable – but needs
Mozilla Firefox; size: 4MB)
Alkasir USB package with Mozilla browser (does not need installation – portable; size: 12MB)
Please note that both versions require the .Net Framework to be installed, which is pre-installed
on all Windows Vista and Windows 7 operating systems.
Optionally, you can register an account to receive regular updates and news from Alkasir by email. Updates are released on a regular basis, so you should be sure to get the latest version
from the official website.
Receive Alkasir by e-mail
If the Alkasir website blocked in your country, you can get the installation file from an e-mail
autoresponder. Simply send a blank email to the address [email protected] to request the
installation file as an attachment.
You will receive an e-mail with the software attached and instructions on how to install Alkasir
on your computer.
If you don't receive the software after a few minutes, you may need to add [email protected] to
your contacts whitelist so the e-mail is not considered as spam.
Once you have downloaded the installation file, double-click on the software icon.
You may get a security warning. Click Run or Accept.
Follow the Alkasir installation wizard by clicking the Next button.
You can change the installation folder (but this is not recommended).
When ready, click Next.
Validate the security warning shown above by clicking Yes.
When the installation is finished, click Close.
Alkasir should start by default whenever Windows is started. Ensure that the software is running
by checking that the Alkasir icon is displayed in your system task bar, near the clock.
Right clicking the icon reveals the configuration menu.
Launch Browser
Open Alkasir interface
Report blocked URLs
The main Alkasir interface gathers all the features from the software. You can do the following:
start, shut down and restart the software
launch the Alkasir browser
register or login on
get updates for your installed version of Alkasir.
First, let's launch the Alkasir browser.
The browser's graphical user interface is very similar to Mozilla Firefox as it is based on the same
technical framework. Note some specific features:
a button for complete Arabic localization
the "Report Blocked URLs" button, to use when you are trying to reach a website that
appears to be blocked. This button is displayed near the address bar and the status bar.
an Alkasir icon to go to the main interface.
You can also find other menus to integrate your Alkasir browser with your Alkasir account.
It is possible to enable or disable the automatic updates for the software, the proxy list and
blocked sites database.
If you are arrive at an error page that could indicate a blocked website (such as an Access
Denied or Connection Timeout error), you can submit this URL to the Alkasir database by clicking
the Report Blocked URL button. You can choose to be notified of the moderator's decision about
whether to enter this URL into the database or not (this decision is based on the tool's policy).
Visit for:
a comprehensive documentation for the software:
a list of Frequently Asked Questions:
Tor (The Onion Router) is a very sophisticated network of proxy servers.
Supported operating
13 languages
Web site
IRC: #tor on
When you use Tor to access a Web site, your communications are randomly routed through a
network of independent, volunteer proxies. All the traffic between Tor servers (or relays) is
encrypted, and each of the relays knows only the IP address of two other machines – the one
immediately previous to it and the one immediately after it in the chain.
The goal of this is unlinkability. Tor makes it very difficult for:
your ISP or any other local observer to know what your target Web site is or what
information you are sending
the target Web site to know who you are (at least, to know your IP address)
any of the independent relays to know who you are and where you go either by directly
having your IP address or by being able to correlate browsing habits by consistently
observing your traffic.
To connect to the Internet through the Tor network and use it for anonymity, privacy, and
circumvention, you need to install the Tor client software on your computer. It is also possible
to run a portable version of the program from a USB flash drive or other external device.
Tor is compatible with most versions of Windows, Mac OS X, and GNU/Linux.
Tor uses a SOCKS proxy interface to connect to applications, so any application that supports
SOCKS (versions 4, 4a and 5) can have its traffic anonymized with Tor, including:
most Web browsers
many instant messaging and IRC clients
SSH clients
e-mail clients.
If you installed Tor from the Vidalia Bundle, Tor Browser Bundle or Tor IM Browser Bundle, Tor
will have also configured an HTTP application proxy as a front-end to the Tor network. This will
allow some applications that do not support SOCKS to work with Tor.
If you are mostly interested in using Tor for Web surfing and chatting, you may find it easiest to
use the Tor Browser Bundle or the Tor IM Browser Bundle which will provide you with ready-touse pre-configured solutions. The Tor Browser Bundle also includes Torbutton, which improves
privacy protection when using Tor with a Web browser. Both versions of Tor can be downloaded
Tor can be a very effective tool for circumvention and protecting your identity. Tor's encryption
hides the contents of your communications from your local network operator, and conceals
whom you are communicating with or what Web sites you're viewing. When used properly, it
provides significantly stronger anonymity protection than a single proxy.
Tor is vulnerable to blocking. Most Tor nodes are listed in a public directory, so it is easy
for network operators to access the list and add the IP addresses of nodes to a filter.
(One way of attempting to get around this kind of blocking is to use one of several Tor
bridges, which are Tor entry nodes not publicly listed, specifically to avoid blocking.)
Some programs you might use with Tor have problems that can compromise anonymity.
The Tor Browser Bundle comes with a version of Firefox with Torbutton installed.
Torbutton disables some plugins and changes your browser fingerprint so it looks like any
other Torbutton user. Tor will not protect you if you do not configure your appplications to
run through Tor. Some plugins and scripts ignore local proxy settings and can reveal your IP
If you're not using additional encryption to protect your communications, your data will be
unencrypted once it reaches the last Tor node in the chain (called an exit node). This
means that your data will be potentially visible to the owner of the last Tor node and to
the ISP between that node and your destination Web site.
The developers of Tor have thought a lot about these and other risks and offer three warnings:
1. Tor does not protect you if you do not use it correctly. Read the list of warnings
here: and then make sure
to follow the instructions for your platform carefully:
2. Even if you configure and use Tor correctly, there are still potential attacks that could
compromise Tor's ability to protect you:
3. No anonymity system is perfect these days, and Tor is no exception: you should not rely
solely on the current Tor network if you really need strong anonymity.
The Tor Browser Bundle lets you use Tor on Windows, OS X, or GNU/Linux without requiring you
to configure a Web browser. Even better, it's also a portable application that can be run from a
USB flash drive, allowing you to carry it to any computer without installing it on each computer's
hard drive.
You can download the Tor Browser Bundle from the Web site, either as a single
file or a "split" version that is multiple files. If your Internet connection is slow and unreliable, the
split version may work better than trying to download one very large file.
If the Web site is filtered from where you are, type "tor mirrors" in your favorite
Web search engine; the results will probably include some alternative addresses to download the
Tor Browser Bundle.
Get Tor through e-mail: send an e-mail to [email protected] with "help" in the message
body, and you will receive instructions on how to have the autoresponder bot send you the Tor
Caution: When you download the Tor Browser Bundle (plain or split versions), you should check
the signatures of the files, especially if you are downloading the files from a mirror site. This step
ensures that the files have not been tampered with. To learn more about signature files and how
to check them, read
You can download the GnuPG software that you will need to check the signature here:
The instructions below refer to installing Tor Browser on Microsoft Windows. If you are using a
different operating system, refer to the Tor Web site for download links and instructions.
Installing from a single file
1. In your Web browser, enter the download URL for Tor Browser:
2. Click the link for your language to download the installation file.
3. Double-click the .exe file that you have now downloaded. A "7-Zip self-extracting archive"
window appears.
1. Choose a folder into which you want to extract the files and click Extract.
Note: you can choose to extract the files directly onto a USB flash drive if you want to
use Tor Browser on different computers (for instance on public computers in Internet
2. When the extraction is completed, open the folder and check that the contents match the
image below:
To clean up, delete the .exe file you originally downloaded.
Installing from split files
1. In your Web browser, enter the URL for the split version of the Tor Browser Bundle
(, then click the link for your
language to get to a page that looks like the one for English below:
2. Click each file to download it (one ending in .exe and nine others ending in .rar), one after
the other, and save them all in one folder on your hard drive.
3. Double-click the first part (the file whose name ends in .exe). This runs a program to
gather all the parts together.
"Split installer for Tor Browser Bundle" src="static/CircumventionToolsInstallingTor-tor_winrar_2-en.png" height="384" width="562">
4. Choose a folder where you want to install the files, and click Install. The program displays
progress messages while it's running, and then quits.
5. When the extraction is completed, open the folder and check that the contents match the
image below:
6. To clean up, delete all the files you originally downloaded.
Before you start:
Close Tor. If Tor is already installed on your computer, make sure it is not currently
Launch the Tor Browser:
In the Tor Browser folder, double-click Start Tor Browser. The Tor control panel (Vidalia) opens
and Tor starts to connect to the Tor network.
When a connection is established, Firefox automatically connects to the TorCheck page and then
confirms that your browser is configured to use Tor. This may take some time, depending on the
quality of your Internet connection.
If you are connected to the Tor network, a green onion icon appears in the system tray on the
lower-right-hand corner of your screen:
Try viewing a few Web sites, and see if they are working. The sites are likely to load more slowly
than usual because your connection is being routed through several relays.
If the onion in the Vidalia Control Panel never turns green or if Firefox opened, but displayed a
page saying "Sorry. You are not using Tor", as in the image below, then you are not using Tor.
If you see this message, close Firefox and Tor Browser and then repeat the steps above. You
can perform this check to ensure that you are using Tor at any time by going to
If Tor Browser doesn't work after two or three tries, Tor may be partly blocked by your ISP and
you should try using the bridge feature of Tor – see the section below on "Using Tor with
The Tor IM Browser Bundle is similar to the Tor Browser Bundle, but includes
access to the Pidgin multi-protocol instant messaging client, so you can chat
encrypted over your favourite instant messenger protocol such as ICQ, MSN
Messenger, Yahoo! Messenger or QQ which may be filtered.
You can learn more about Pidgin here:
You can download the Tor IM Browser Bundle directly from the Tor Web site
If your Internet connection is slow or unreliable, you can also get a split up version on the Web site at
To get started, double-click the .exe file you have downloaded.
You should see the window below:
Choose a folder into which you want to extract the files. If you are not sure leave the
default value untouched. Then click Extract.
Note: you can choose to extract the files directly onto a USB flash drive if you want
to use Tor Browser on different computers (for instance on public computers in
Internet cafés).
When the extraction is completed, open the newly-created folder and check that it looks
like the image below (note the PidginPortable folder):
You can now safely delete the .exe file you originally downloaded (or the several .rar and
.exe files if you used the split version).
Before you start:
Close Firefox. If the Firefox browser is installed on your computer, make sure it is not
currently running.
Close Tor. If Tor is already installed on your computer, make sure it is not currently
Launch Tor IM Browser:
In the Tor Browser folder, double-click Start Tor Browser. The Tor control panel (Vidalia)
opens and Tor connects to the Tor network.
When a connection is established:
A Firefox browser window pops up and connects to the TorCheck page, which should show
a green onion that confirms you that your browser is configured to use Tor.
A Pidgin assistant window (below) pops up inviting you to set up your IM account on Pidgin.
You will also see the Tor icon (a green onion if you are connected) and a Pidgin icon appear in the
system tray on the lower right corner of your screen:
You can set up your IM account in the Pidgin window. Pidgin is compatible with most major IM
services (AIM, MSN, Yahoo!, Google Talk, Jabber, XMPP, ICQ and others):
To learn more on how you can use Pidgin, read:
If the onion in the Vidalia Control Panel doesn't turn green or if Firefox opens, but displays a page
saying "Sorry. You are not using Tor", then you should:
Exit Vidalia and Pidgin (see below for details).
Relaunch Tor IM Browser following the steps above ("Using Tor IM Browser Bundle").
If Tor Browser still doesn't work after two or three tries, Tor may be partly blocked by your ISP.
Refer to the "Using Tor with Bridges" section below to use the bridge feature of Tor.
To exit the Tor IM Browser you need to:
Exit Vidalia by right-clicking on the onion icon in your tray bar and choosing Exit in the
Vidalia contextual menu.
Exit Pidgin by right-clicking on the Pidgin icon in your tray bar and choosing Quit in the
Pidgin contextual menu.
When the Vidalia onion icon and the Pidgin icon have disappeared from the Windows system tray
in the lower-right-hand corner of your screen, Tor IM Browser is closed.
If you suspect your access to the Tor network is being blocked, you may want to use the bridge
feature of Tor. The bridge feature was created specifically to help people use Tor from places
where access to the Tor network is blocked. You must already have successfully downloaded
and installed the Tor software to use a bridge.
Bridge relays (or bridges for short) are Tor relays that aren't listed in the main public Tor
directory. This is a deliberate measure to stop these relays from being blocked. Even if your ISP
is filtering connections to all the publicly known Tor relays, it may not be able to block all the
To use a bridge, you need to locate one and add its information in your network settings. A
simple way to get a few bridges is by simply accessing with your
Web browser. If that Web site is blocked or you need more bridges, send an e-mail from a Gmail
account to [email protected] with "get bridges" (without the quotemarks) in the body of the
Almost instantly, you will receive a reply that includes information about a few bridges:
Important Notes:
1. You must use a Gmail account to send the request. If accepted requests
from other mail accounts, an attacker could easily create a lot of email addresses and
quickly learn about all the bridges. If you do not have a Gmail account already, creating one
takes only a few minutes.
2. If you are on a slow Internet connection you can use the URL for a direct access to the basic HTML version of Gmail.
After you get addresses for some bridge relays, you must configure Tor with whatever bridge
address you intend to use:
1. Open the Tor control panel (Vidalia).
2. Click Settings. A Settings window opens.
3. Click Network.
4. Select "My Firewall only lets me connect to certain ports" and "My ISP blocks connections
to the Tor network".
5. Enter the bridge URL information you received by e-mail in the "Add a Bridge" field.
6. Click the green + on the right side of the "Add a Bridge" field. The URL is added to the box
7. Click OK at the bottom of the window to validate your new settings.
8. In the Tor control panel, stop and restart Tor to use your new settings.
Add as many bridge addresses as you can. Additional bridges increase reliability. One bridge is
enough to reach the Tor network, however if you have only one bridge and it gets blocked or
stops operating, you will be cut off from the Tor network until you add new bridges.
To add more bridges in your network settings, repeat the steps above with the information on
the additional bridges that you got from the [email protected] e-mail message.
JonDo started as a German university project called Java Anon Proxy (JAP) and has become a
robust anonymity tool that, like Tor, sends traffic through several independent servers.
Unlike Tor, however, the JonDo network mixes servers run by volunteers with others maintained
by a parent company. The arrangement gives users a choice of speeds: 30-50 kBit/s (about the
speed of an analog modem connection) for free, >600 kBit/s for a fee. For a more detailed
comparison and price list, see:
Supported operating
English, German, Czech, Dutch, French and Russian
Web site
Contact form:
To use the JonDo network, called JonDonym, you'll need to download the JonDo client for your
operating system from Versions are available for Linux
(about 9 MB), Mac OS X (about 17 MB) and Windows (about 35 MB).
Once you have download the client, install it as you would any software for your platform. You
may be asked if you wish to install it on your PC or if you wish to create a portable version. For
our example, we will assume you are installing JonDo on a PC.
Windows users also may be invited to install the JonDoFox web browser, discussed below.
When you first start JonDo, you can choose the language you want displayed.
Next, you can choose the level of detail you wish to see when using the service. Inexperienced
users should choose "Simplified view".
On the next screen, the Installation assistant asks you to choose the Web browser that you
want to use the JonDo proxy tool. Click on the name of your browser, and follow the instructions.
Once that is completed, JonDo asks you to test your configuration. In the control panel, switch
anonymity to Off and then try opening a Web site with the browser you have just configured.
If JonDo shows you a warning and you have to choose "Yes" to view the Web site, everything is
configured properly and you can select "The warning is shown. Websurfing is possible after
confirmation". If any other description applies to you, choose it and the Installation assistant will
give you more information on how to solve the problem.
Now take the second step to insure a proper configuration: Switch anonymity to "On" in the
control panel and open a random Web site with the browser you have configured.
If the Web site loads, everything is fine and you can click "Connection established, websurfing is
fine". If another description applies to you choose that one and the Installation assistant will help
you solve the problem.
We're almost done. You have successfully configured your browser to connect through the JonDo
network. Now, you should also configure your browser so that it doesn't accidentally leak any
information. Click on the name of your browser to start the process.
If the standard JonDo servers are already blocked in your country, you should try the anticensorship option. Click "Config" in the control panel and select the Network tab. Click on
"Connect to other JAP/JonDo users in order to reach the anonymization service". Read the
warning and confirm by clicking "Yes".
To make sure you configured your browser correctly, you can point it to which will tell you if there is any problem.
For additional security, the JonDoNym team offers a modified Firefox Web browser called
JonDoFox. Similar to the Tor browser bundle, it prevents leaking additional information while using
the anonymization tool.
You can download the tool at
Your-Freedom is a commercial proxy tool that also offers a free (though slower) service.
The software is available for Microsoft Windows, Linux and Mac OS and connects you to a
network of about 30 servers across ten countries. Your-Freedom also offers advanced services
like OpenVPN and SOCKS, making it a relatively sophisticated tool to bypass Internet censorship.
operating system
20 languages
Web site
User guide:
First, download the tool for free from If
you already have Java installed, you can download the small version which is about 2 MB. To
check whether Java is installed, visit If you don't
have Java installed, download the full installer, which is about 12 MB. All files are also available
If you live in a country where the government censors access to the Internet, Your-Freedom
may work for you with the Sesawe account (username: sesawe, password: sesawe). If that
doesn't work you have to register for a account. To get started, register a free account on the
Web site
Click the "First visit? Click here to register" link below the two login fields.
On the next page, enter the required information. Only a username, password, and e-mail
address are needed. Other information is optional.
You’ll see a message that your registration is almost complete and within a few seconds, you
should receive an e-mail at the address you provided.
Click the second link (the longer one) to confirm your registration.
When you see the "Thank you" screen, your account has been activated.
The following instructions and screenshots have been captured under Windows, but all the steps
and settings are very similar for other operating systems.
Now you are ready to install Your-Freedom.
Click on the downloaded file. The file name may vary as new versions are released on a regular
Click Next in the first screen.
In the next screen you can choose if the program should be usable only for your account only or
for all users of your computer (common). Then click Next.
Choose the directory for installing Your-Freedom. Most users should accept the default selection.
Click Next.
On the next screen of the installer you can alter the name which will be used in the program
folder. You can leave the default untouched and click Next.
Choose whether you want to create an icon on the desktop. Click Next again.
Here you can see a summary of the decisions you made. Confirm them by clicking Next, or go
back if anything needs changing.
Now the installation takes place. This may take a few minutes, depending on your PC.
Finally the installation is ready. Quit the installation program by clicking Finish.
Your-Freedom will start automatically. When you later want to start it manually click on the
Your-Freedom icon (the door) on your desktop.
When you first start Your-Freedom you need to configure it.
The first step is to choose your language. Click on the language you want. You will be able to
change the settings later.
Right after the first start you will see the configuration wizard. Click Next.
In the Proxy Server dialog the program will auto-detect the information of a proxy server you
can use. Click Next.
In the Select Protocols dialog you should keep the default values and proceed by clicking Next.
Now the Your-Freedom configuration wizard will make several tests to find available servers and
check your type of connection and filtering. This may take some minutes.
You may get an warning from your firewall (here, for example the one from Windows 7). You can
allow access to Your-Freedom.
When the wizard is ready you see the Found Freedom Servers screen where you can choose one
server and click Next again.
Now enter your previously created account information. If you don't have one, you can get a
free access by sending a request to the email address: [email protected]
Click Next.
When you see the "Congratulations!" screen, the configuration wizard is ready. Click on Save and
Your-Freedom is now running on your computer, and you can see an icon in your task bar.
For additional security and better ways to bypass filters you should tweak the options by clicking
on Configure in the main Your-Freedom window and selecting the options shown in the
screenshot below. Then click Save and Exit.
Now Your-Freedom is connected to a server and provides a local proxy that you can use with
your preferred software such as Internet Explorer or Firefox. To automatically configure them,
click on the Application tab in the main Your-Freedom window, select which software you want
to use and click OK. Your-Freedom will automatically configure that software so that it connects
over the encrypted Your-Freedom tunnel to the Internet.
To make sure you are using Your-Freedom correctly go to the
Web site and check the Your Footprint section on the left. If the country detected is not where
you are, you are successfully using the encrypted Your-Freedom tunnel to access the Internet.
27. Domains and DNS
28. HTTP Proxies
29. The Command Line
30. OpenVPN
31. SSH Tunnelling
32. SOCKS Proxies
If you have identified, suspect or were told that the main censorship technique on your network
is based on DNS filtering and spoofing, you should consider these techniques.
Simply speaking, a DNS server translates a human-friendly Internet address such as
into the IP address, such as, that identifies the specific server or servers on the
Internet associated with that name. This service is most often accessed through DNS servers
maintained by your Internet Service Provider (ISP). Simple DNS blocking is implemented by giving
an incorrect or invalid response to a DNS request, in order to prevent users from locating the
servers they're looking for. This method is very easy to implement on the censor side, so it is
widely used. Keep in mind that often there are several censorship methods are combined, so
DNS blocking may not be the only problem.
You can potentially bypass this type of blocking in two ways: by changing your computer's DNS
settings to use alternative DNS servers, or by editing your hosts file.
You can bypass the DNS servers of your local ISP, using third-party servers to let your computer
find the addresses of domains that may be blocked by the ISP's DNS servers. There are a
number of free, internationally available DNS services that you can try. OpenDNS
( provides one such service and also maintains guides on how to
change the DNS server that your computer uses
( There is also an updated list of available DNS
servers from around the world at
Here is a list of publicly-available DNS services, via the Internet Censorship Wiki at (Some of these services may themselves block a limited number of
sites; consult the providers' sites to learn more about their policies.)
Publicly-available DNS servers
DNS Advantage
DNS Advantage
Level 3
Cable & Wireless
Once you've chosen a DNS server to use, you need to enter your selection into your operating
system's DNS settings.
Change your DNS settings in Windows
1. Open your control panel under the Start menu.
2. Under Network and Internet, click on "View network status and stats".
3. Click on your wireless connection at the right side of the window.
4. The Wireless Network Connection Status window will open. Click on Properties.
5. In the Wireless Network Connection Properties window select Internet Protocol Version 4
(TCP/IPv4), and click on Properties.
6. You should now be in the Internet Protocol Version 4 (TCP/IPv4) Properties window, where
you are going to specify your alternate DNS address (for example: Google Public DNS)
7. At the bottom of the window, click on "Use the following DNS server addresses" and
complete the fields with your preferred and alternate DNS server IP information. When you
are done, click OK. By default the first DNS server will be used. The alternate DNS server
can be from another company.
Change your DNS settings in Ubuntu
1. In the System menu go to Preferences > Network Connections.
2. Select the connection for which you want to configure Google Public DNS. If you want to
change the settings for an Ethernet connection (cable), select the Wired tab, then select
your network interface in the list. If you want to change the settings for a wireless
connection instead, select the Wireless tab, then select the appropriate wireless network.
3. Click Edit, and in the window that appears, select the IPv4 Settings tab
4. If the selected method is Automatic (DHCP), open the dropdown menu and select
"Automatic (DHCP) addresses only" instead. If the method is set to something else, do not
change it.
5. In the DNS servers field, enter your alternate DNS IP information, separated by a space.
For example, if you want to add Google DNS write:
6. Click Apply to save the changes. If you are prompted for a password or confirmation, type
the password or confirm that you want to make the changes.
7. Repeat steps 1-6 for every network connection you want to modify.
If you know the IP address of one particular web site or other Internet service that is blocked by
your ISP's DNS servers, you can list this site in your own computer's hosts file, which is a local
list of name-to-IP address equivalents that your computer will use before checking external DNS
servers. The hosts file is a text file with an extremely simple format; its contents look like:
where each line contains an IP address, then a space, and then a name. You can add any number
of sites to your hosts file (but note that if you use the wrong address for a site, it could prevent
you from accessing that site by name until you fix it or remove it from the list).
If you can't find a site's IP address because of your ISP's DNS blocking, there are hundreds of
services that will help you do an uncensored DNS lookup. For example, you could use any of the
tools at
You could also consider using the tools at, which are sophisticated
network diagnostic tools provided by various ISPs. They were originally intended for diagnosing
accidental network outages rather than intentional censorship, but they can be useful for
diagnosing censorship too. These tools also include the ability to look up the IP address of a
particular server.
Edit your hosts file in Windows Vista / 7
You will need to use a simple text editor, such as Notepad, to edit your hosts file. In Windows
Vista and 7, your hosts file is usually located at C:\Windows\system32\drivers\etc\hosts.
1. Click on the Start button.
2. Type "notepad" at the search box.
3. Once you found the program, right-click on it and select "Run as administrator"
4. Windows will ask for your permission to make changes to files. Click Yes.
5. Under the File menu, select Open.
6. Browse to C:\Windows\System32\Drivers\etc\. You may notice that the folder seems
initially empty.
7. At the bottom right of the open dialog, select All Files.
8. Select the file "hosts" and click Open.
9. Add for example the line "" at the end of the file and save
it by pressing Ctrl+S or by selecting File > Save from the menu.
Edit your hosts file in Ubuntu
In Ubuntu, your hosts file is located in /etc/hosts. To edit it, you will need to have some
knowledge of the command line. Please refer to the chapter "The Command Line" in this book
for a brief tutorial on this feature.
1. Open the terminal by going to Accessories > Terminal under your Applications menu.
2. Use the following command line to automatically add a line to your hosts file:
echo | sudo tee -a /etc/hosts
3. You may be prompted for your password in order to modify the file. Once authorized, the
command will append "" to the the last line of the hosts
4. Optional: if you feel more comfortable working in a graphical interface, open the terminal
and use the following command line to launch a text editor:
sudo gedit /etc/hosts
5. You may be prompted for your password in order to modify the file. Once the window has
opened, simply add the line "" at the end of the file, and
save it by pressing Ctrl+S or selecting File > Save from the menu.
Software called an application proxy enables one computer on the Internet to process requests
from another computer. The most common kinds of application proxies are HTTP proxies, which
handle requests for Web sites, and SOCKS proxies, which handle connection requests from a
wide variety of applications. In this chapter we will look at HTTP proxies and how they work.
Application proxies can be used by network operators to censor the Internet or to monitor and
control what users do. However, application proxies are also a tool for users to get around
censorship and other network restrictions.
Proxies that restrict access
A network operator may force users to access the Internet (or at least Web pages) only through
a certain proxy. The network operator can program this proxy to keep records of what users
access and also to deny access to certain sites or services (IP blocking or port blocking). In this
case, the network operator may use a firewall to block connections that do not go through the
restrictive proxy. This configuration is sometimes called a forced proxy, because users are
required to use it.
Proxies for circumvention
However, an application proxy can also be helpful for circumventing restrictions. If you can
communicate with a computer in an unrestricted location that is running an application proxy,
you can benefit from its unrestricted connectivity. Sometimes a proxy is available for the public
to use; in that case, it's called an open proxy. Many open proxies are blocked in Internetrestricting countries if the people administering the network restrictions know about them.
There are many Web sites with lists of open application proxies. An overview of such sites is
available at
Please note that many open application proxies only exist for a few hours, so it is important to
get a proxy from a list which was very recently updated.
To use an application proxy, you must configure the proxy settings for your operating system or
within individual applications. Once you have selected a proxy in an application's proxy settings,
the application tries to use that proxy for all of its Internet access.
Be sure you make note of the original settings so that you can restore them. If the proxy
becomes unavailable or unreachable for some reason, the software that is set to use it generally
stops working. In that case, you may need to reset to the original settings.
On Mac OS X and some Linux systems, these settings can be configured in the operating system,
and will automatically be applied to applications such as the web browser or instant messaging
applications. On Windows and some Linux systems, there is no central place to configure proxy
settings, and each application must be configured locally. Bear in mind that, even if the proxy
settings are configured centrally, there is no guarantee that applications will support these
settings, so it is always a good idea to check the settings of each individual application.
Typically only Web browsers can directly use an HTTP proxy.
The steps below describe how to configure Microsoft Internet Explorer, Mozilla Firefox, Google
Chrome and the free and open source instant messaging client Pidgin to use a proxy. If you use
Firefox for Web browsing, it may be simpler to use the FoxyProxy software; it is an alternative
to the steps below. If you use Tor, it is safest to use the TorButton software (which is provided
as part of the Tor Bundle download) to configure your browser to use Tor.
While e-mail clients such as Microsoft Outlook and Mozilla Thunderbird can also be configured to
use HTTP proxies, actual e-mail traffic when sending and fetching e-mail uses other protocols
such as POP3, IMAP and SMTP; this traffic will not pass through the HTTP proxy.
Mozilla Firefox
To configure Firefox to use an HTTP proxy:
1. Select Tools > Options:
2. The Options window appears:
3. In the toolbar at the top of the window, click Advanced:
4. Click the Network tab:
5. Click Settings. Firefox displays the Connection Settings window:
6. Select "Manual proxy configuration". The fields below that option become available.
7. Enter the HTTP proxy address and port number, and then click OK.
If you click "Use this proxy server for all protocols", Firefox will attempt to send HTTPS (secure
HTTP) and FTP traffic through the proxy. This may not work if you are using a public application
proxy, since many of these do not support HTTPS and FTP traffic. If, on the other hand your
HTTPS and/or FTP traffic is being blocked, you can try to find a public application proxy with
HTTPS and/or FTP support, and use the "Use this proxy server for all protocols" setting in
Now Firefox is configured to use an HTTP proxy.
Microsoft Internet Explorer
To configure Internet Explorer to use an HTTP proxy:
1. Select Tools > Internet Options:
2. Internet Explorer displays the Internet Options window:
3. Click the Connections tab.
4. Click LAN Settings. The Local Area Network (LAN) Settings window appears.
5. Select "Use a proxy server for your LAN".
6. Click Advanced. The Proxy Settings window appears.
7. Enter the proxy address and port number in the first row of fields.
8. If you click "Use the same proxy server for all protocols", Internet Explorer will attempt to
send HTTPS (secure HTTP) and FTP traffic through the proxy. This may not work if you are
using a public application proxy, since many of these do not support HTTPS and FTP traffic.
If, on the other hand your HTTPS and/or FTP traffic is being blocked, you can try to find a
public application proxy with HTTPS and/or FTP support, and use the "Use this proxy
server for all protocols" setting in Internet Explorer.
Now Internet Explorer is configured to use an HTTP proxy.
Google Chrome
Google Chrome uses the same connection and proxy settings as the Windows operating system.
Changing these settings affects Google Chrome as well as Internet Explorer and other Windows
programs. If you configured your HTTP proxy through Internet Explorer then you don't need to
take this steps to configure Chrome.
Follow these steps to configure your HTTP proxy:
1. Click on the "Customize and control Google Chrome" menu (the little wrench next to the
URL address bar):
2. Click on Options:
3. In the Google Chrome Options window, select the Under the Hood tab:
4. In the Network section, click the "Change proxy settings" button:
5. The Internet Options window will open. Follow steps 2-8 from "How to configure the HTTP
Proxy under Internet Explorer" (above) to finish setting up your HTTP proxy.
Chrome is now configured to use HTTP proxy.
Pidgin instant messaging client
Some Internet applications other than Web browsers can also use a HTTP proxy to connect to
the Internet, potentially bypassing blocking. Here is an example with the instant messaging
software Pidgin.
1. Select Tools > Preferences:
Pidgin displays the Preferences window:
2. Click the Network tab:
3. For Proxy type, select HTTP. Additional fields appear under that option.
4. Enter the Host address and port number of your HTTP proxy.
5. Click Close.
Pidgin is now configured to use the HTTP proxy.
When you're done with the proxy
When you are done using a proxy, particularly on a shared computer, return the settings you've
changed to their previous values. Otherwise, those applications will continue to try to use the
proxy. This could be a problem if you don't want people to know that you were using the proxy
or if you were using a local proxy provided by a particular circumvention application that isn't
running all the time.
Before continuing with the rest of the book it is good to know something about how the
command line works. If you are not familiar with the command line the following is intended to
get you uptodate in the basics quickly.
Although interactions on a computer happen so fast you don't think about it, each click or
keystroke is a command to the computer, which it reacts to. Using the command line is the
same thing, but more deliberate. You type a command and press the Return or Enter key. For
instance, in my terminal I type:
And the computer replies with:
Fri Feb 25 14:28:09 CET 2011
That's pretty computerish. In later chapters we'll explain how to request the date and time in a
more congenial format. We'll also explain how working in different countries and with different
languages changes the output. The idea for now is that you've just had an interaction.
The date command, as seen so far, compares poorly with the alternative of glancing at a
calendar or clock. The main problem is not the unappetizing appearance of the output,
mentioned already, but the inability to do anything of value with the output. For instance, if I'm
looking at the date in order to insert it into a document I'm writing or update an event on my
online calendar, I have to do some retyping. The command line can do much better than this.
After you learn basic commands and some useful ways to save yourself time, you'll find out
more in this book about feeding the output of commands into other commands, automating
activities, and saving commands for later use.
At the beginning of this chapter we used the word command very generally to refer to any way
of telling the computer what to do. But in the context of this book, a command has a very
specific meaning. It's a file on your computer that can be executed, or in some cases an action
that is built into the shell program. Except for the built-in commands, the computer runs each
command by finding the file that bears its name and executing that file. We'll give you more
details as they become useful.
To follow along on this book, you need to open a command-line interpreter or command-line
interface (called a shell or terminal in GNU/Linux) on your computer. Pre-graphical computer
screens presented people with this interpreter as soon as they logged in. Nowadays almost
everybody except professional system administrators uses a graphical interface, although the
pre-graphical one is still easier and quicker to use for many purposes. So we'll show you how to
pull up a shell.
You can get a terminal interface from the desktop, but it may be easier to leave the desktop
and use the original text-only terminal. To do that, use the < ctrl + alt + F1 > key combination.
You get a nearly blank screen with an invitation to log in. Give it your username and password.
You can go to other terminals with < alt + F2 > and so on, and set up sessions with different (or
the same) users for whatever tasks you want to do. At any time, switch from one to another by
using the < alt + F# > keystroke for the one you want. One of these, probably F7 or F8, will get
you back to the desktop. In text terminals you can use the mouse (assuming your system has
gpm running) to select a word, line or range of lines. You can then paste that text somewhere
else in that or any other terminal.
GNU/Linux distributions come with different graphical user interfaces (GUI) offering different
aesthetics and semantic metaphors. Those running on top of the operating system are known as
desktop environments. GNOME, KDE and Xfce are among the most widely used. Virtually every
desktop environment provides a program that mimics the old text-only terminals that
computers used to offer as interfaces. On your desktop, try looking through the menus of
applications for a program called Terminal. Often it's on a menu named something such as
Accessories, which is not really appropriate because once you read this book you'll be spending a
lot of time in the terminal every day.
In GNOME you select Applications > Accessories > Terminal.
In KDE, select K Menu -> System -> Terminal.
In Xfce, select Xfce Menu -> System -> Terminal.
Wherever it's located, you can almost certainly find a terminal program.
When you run the terminal program, it just shows a blank window; there's not much in the way
of help. You're expected to know what to do – and we'll show you.
The following figure shows the Terminal window opened on the desktop in GNOME.
Many graphical interfaces also provide a small dialog box called something like "Run command". It
presents a small text area where you can type in a command and press the Return or Enter
To invoke this dialog box, try typing the < alt + F2 > key combination, or searching through the
menus of applications. You can use this box as a shortcut to quickly start up a terminal program,
as long as you know the name of a terminal program installed on your computer. If you are
working on an unfamiliar computer and don't know the name of the default terminal program,
try typing xterm to start up a no-frills terminal program (no fancy menus allowing choice of color
themes or fonts). If you desperately need these fancy menus,
in GNOME the default terminal program should be gnome-terminal
in KDE it should be konsole
in Xfce try Terminal or version specific terminal names, for example in Xfce 4 you should
find xfce4-terminal .
OpenVPN is a well-respected, free, open source Virtual Private Network (VPN) solution. It works
on most versions of Windows (Windows Vista support is expected soon), Mac OS X and Linux.
OpenVPN is SSL-based, which means it uses the same type of encryption that is used when
visiting secure Web sites where the URL starts with https.
Supported operating system
English, German, Italian, French and Spanish
Web site
OpenVPN is not suitable for temporary use in Internet cafés or elsewhere on shared computers
where you can't install additional software.
For a more general presentation of VPNs and ready-to-use VPN services, read the "VPN
Services" chapter in this manual.
In an OpenVPN system, there is one computer set up as a server (in an unrestricted location),
and one or more clients. The server must be set up to be accessible from the Internet, not
blocked by a firewall and with a publicly routable IP address (in some places, the person
establishing the server may have to request this from their ISP). Each client connects to the
server and creates a VPN tunnel through which traffic from the client can pass.
There are commercial OpenVPN providers such as WiTopia (
where you can purchase access to an OpenVPN server for a fee of about 5-10 US dollars a
month. These providers will also help you install and configure OpenVPN on your computer. A list
of such commercial providers is available at
OpenVPN also can be used by a trusted contact in an unfiltered location, providing an OpenVPN
server to one or more clients and passing their traffic to his/her computer before continuing on
to the Internet. Setting this up correctly is somewhat complicated, however.
To setup your own OpenVPN server and client, follow the documentation provided by OpenVPN
( If you want to use OpenVPN to visit
blocked Web sites, the following notes are important:
There is a graphical user interface (GUI) available for Windows which will make it easy to start
and stop OpenVPN as required, and also enables you to configure OpenVPN to use an HTTP
proxy to get onto the Internet. To download the GUI go to
To configure OpenVPN to use a proxy server in Linux or Mac OS X, read the relevant section on
the Web site (
When choosing between routing and bridging, there is no additional advantage in configuring
bridging when your clients just want to use it to bypass Internet censorship. Choose
Pay special attention to the section of the guide that explains how to ensure that all traffic
from the client is passed through the server. Without this configuration the system will not
help you to visit blocked Web pages
If the client computer is behind a very restrictive firewall, and the default OpenVPN port is
blocked, it is possible to change the port that OpenVPN uses. One option is to use port
443, which is normally used for secure websites (HTTPS), and to switch to TCP protocol
instead of UDP. In this configuration, it is difficult for firewall operators to differentiate
between OpenVPN traffic and normal secure Web traffic. To do this, near the top of the
configuration files on both the client and server, replace "proto udp" with "proto tcp" and
"port 1194" with "port 443".
Once it is set up and configured correctly, OpenVPN can provide an effective way to bypass
Internet filters. Since all traffic is encrypted between the client and the server, and can pass
through a single port, it is very difficult to distinguish from any other secure Web traffic, such as
data going to an online shopping site or other encrypted services.
OpenVPN can be used for all Internet traffic, including Web traffic, e-mail, instant messaging and
OpenVPN also provides a degree of protection against surveillance, as long as you can trust the
owner of the OpenVPN server, and you have followed the instructions in the OpenVPN
documentation on how to handle the certificates and keys used. Remember that traffic is only
encrypted as far as the OpenVPN server, after which it passes unencrypted onto the Internet.
The primary disadvantage of OpenVPN is the difficulty of installation and configuration. It also
requires access to a server in an unrestricted location. OpenVPN also does not reliably provide
SSH, the Secure Shell, is a standard protocol that encrypts communications between your
computer and a server. The encryption prevents these communications from being viewed or
modified by network operators. SSH can be used for a wide variety of secure communications
applications, where secure log-in to a server and secure file transfers (scp or SFTP) are the most
SSH is especially useful for censorship circumvention because it can provide encrypted tunnels
and work as a generic proxy client. Censors may be reluctant to block SSH entirely because it is
used for many purposes other than circumventing censorship; for example, it is used by system
administrators to administer their servers over the Internet.
Using SSH requires an account on a server machine, generally a Unix or Linux server. For
censorship circumvention, this server needs to have unrestricted Internet access and, ideally, is
operated by a trusted contact. Some companies also sell accounts on their servers, and many
Web hosting plans provide SSH access. There is a list of shell account providers at: which sell
accounts for about 2-10 US dollars a month.
An SSH program called OpenSSH is already installed on most Unix, Linux, and Mac OS computers
as a command-line program run from a terminal as "ssh". For Windows, you can also get a free
SSH implementation called PuTTY.
All recent versions of SSH support creating a SOCKS proxy that allows a Web browser and a
wide variety of other software to use the encrypted SSH connection to communicate with the
unfiltered Internet. In this example, we will describe only this use of SSH. The steps below will set
up a SOCKS proxy on local port 1080 of your computer.
OpenSSH is available from, but it comes pre-installed on Linux/Unix
and Mac OS computers.
The ssh command you'll run contains a local port number (typically 1080), a server name, and a
username (account name). It looks like this:
ssh -D localportnumber [email protected]
For example:
You'll be prompted for your password and then you'll be logged into the server. With the use of
the -D option, a local SOCKS proxy will be created and will exist as long as you're connected to
the server. Important: you should now verify the host key and configure your applications,
otherwise you are not using the tunnel you have created!
PuTTY is available from :
You can save the putty.exe program on your hard drive for future use, or run it directly from
the Web site (often, this is possible on a shared or public-access computer, such as a computer
in a library or Internet café).
When you start PuTTY, a session configuration dialog appears. First enter the host name
(address) of the SSH server you are going to connect to (here, If you only know
the IP address or if DNS blocking is preventing you from using the host name, you can use the IP
address instead. If you will perform these steps frequently, you can create a PuTTY profile that
saves these options as well as the options described below so they will be used every time.
Next, in the Category list, select Connection > SSH > Tunnels.
Enter 1080 for the Source port, and check the Dynamic and IPv4 boxes.
Now click Add, and then Open. A connection is established to the server, and a new window
opens, prompting you for your username and password.
Enter this information and you will be logged into the server and receive a command line prompt
from the server. The SOCKS proxy is then established. Important: you should now verify the
host key and configure your applications, otherwise you are not using the tunnel you have
The first time you connect to a server, you should be prompted to confirm the host key
fingerprint for that server. The host key fingerprint is a long sequence of letters and numbers
(hexadecimal) like 57:ff:c9:60:10:17:67:bc:5c:00:85:37:20:95:36:dd that securely identifies a
particular server. Checking the host key fingerprint is a security measure to confirm that you
are communicating with the server you think you are, and that the encrypted connection cannot
be intercepted.
SSH does not provide a means of verifying this automatically. To get the benefit of this security
mechanism, you should try to check the value of the host key fingerprint with the administrator
of the server you're using, or ask a trusted contact to try connecting to the same server to see
if they see the same fingerprint.
Verifying host key fingerprints is important for ensuring that SSH protects the privacy of your
communications against eavesdropping, but it isn't necessary if you only want to circumvent
censorship and don't care if network operators can see the contents of your communications.
The proxy created by the steps above should work until you close the SSH program. However, if
your connection to the server is interrupted, you will need to repeat the same steps to
reactivate the proxy.
Once the proxy is up and running, you need to configure software applications to use it. Using
the steps above, the proxy will be a SOCKS proxy located on localhost, port 1080 (also known as, port 1080). You should try to ensure that your applications are configured in a way that
prevents DNS leaks, which could make SSH less effective both for privacy protection and
censorship circumvention.
So far, all these commands display a command line on the remote machine from which you can
then execute whatever commands that machine provides to you. Sometimes you may want to
execute a single command on a remote machine, returning afterward to the command line on
your local machine. This can be achieved by placing the command to be executed by the remote
machine in single quotes.
$ ssh [email protected] 'mkdir /home/myname/newdir'
what you need is to execute time consuming commands on a remote machine, but
you aren't sure to have sufficient time during your current ssh session. If you close the remote
connection before a command execution has been completed, that command will be aborted. To
avoid losing your work, you may start via ssh a remote screen session and then detach it and
reconnect to it whenever you want. To detach a remote screen session, simply close the ssh
connection: a detached screen session will remain running on the remote machine.
offers many other options. You can also set up your favorite systems to allow you to log in
or run commands without specifying your password each time. The setup is complicated but can
save you a lot of typing; try doing some Web searches for "ssh-keygen", "ssh-add", and
The SSH protocol extends beyond the basic ssh command. A particularly useful command based
on the SSH protocol is scp , the secure copy command. The following example copies a file from
the current directory on your local machine to the directory /home/me/stuff on a remote
$ scp [email protected]:/home/me/stuff
Be warned that the command will overwrite any file that's already present with the name
/home/me/stuff/ (Or you'll get an error message if there's a file of that name and you
don't have the privilege to overwrite it.) If /home/me is your home directory, the target directory
can be abbreviated.
$ scp [email protected]:stuff
You can just as easily copy in the other direction: from the remote machine to your local one.
$ scp [email protected]:docs/interview.txt yesterday-interview.txt
The file on the remote machine is interview.txt in the docs subdirectory of your home directory.
The file will be copied to yesterday-interview.txt in the home directory of your local system
can be used to copy a file from one remote machine to another.
$ scp [email protected]:file1 [email protected]:otherdir
To recursively copy all of the files and subdirectories in a directory, use the -r option.
$ scp -r [email protected]:dir1 [email protected]:dir2
See the scp man page for more options.
is a very useful command that keeps a remote directory in sync with a local directory. We
mention it here because it's a useful command-line way to do networking, like ssh , and because
the SSH protocol is recommended as the underlying transmission for rsync .
The following is a simple and useful example. It copies files from your local /home/myname/docs
directory to a directory named backup/ in your home directory on the system rsync actually minimizes the amount of copying necessary through various
sophisticated checks.
$ rsync -e ssh -a /home/myname/docs [email protected]:backup/
The -e option to ssh uses the SSH protocol underneath for transmission, as recommended. The a option (which stands for "archive") copies everything within the specified directory. If you want
to delete the files on the local system as they're copied, include a --delete option.
If you use SSH to connect to a lot of different servers, you will often make mistakes by
mistyping usernames or even host names (imagine trying to remember 20 different
username/host combinations). Thankfully, SSH offers a simple method to manage session
information through a configuration file.
The configuration file is hidden in your home directory under the directory .ssh (the full path
would be something like /home/jsmith/.ssh/config – if this file does not exist you can create it).
Use your favorite editor to open this file and specify hosts like this:
Host dev
User fc
You can set up multiple hosts like this in your configuration file, and after you have saved it,
connect to the host you called "dev" by running the following command:
$ ssh dev
Remember, the more often you use these commands the more time you save.
SOCKS is an Internet protocol which presents a special kind of proxy server. The default port
for SOCKS proxies is 1080, but they may also be available on other ports. The practical
difference to normal HTTP proxies is that SOCKS proxies work not only for Web browsing, but
also for other applications like video games, file transfer or instant messenger clients. Similar to
a VPN, they work as a secure tunnel.
Common SOCKS versions include 4, 4a and 5. The version 4 always needs the IP address to
create a connection, so the DNS resolution still has to take place on the client. This make it
useless for many circumvention needs. Version 4a usually uses hostnames. Version 5 includes
newer techniques such as authentication, UDP and IPv6, but it often uses IP addresses, so it
might also not be the perfect solution. See also the section "DNS leaks" at the end of this
A variety of software can take advantage of a SOCKS proxy to bypass filters or other
restrictions not only Web browsers, but also other Internet software like instant messaging and
e-mail applications.
Although public SOCKS proxies do exist, in many cases SOCKS proxies will run locally on your
computer, and will be provided by a software application. Because SOCKS tunnels are so flexible,
some censorship circumvention software creates a local proxy running on your own computer
(which is usually referred to by the name localhost or the IP address This local proxy is
a way to let applications such as a Web browser take advantage of the circumvention software.
Tools that can work in this way include Tor, Your-Freedom and SSH tunnels set up with PuTTY.
Local proxy enthusiast T-shirt (get it?)
In order to use an application proxy for circumventing censorship, you must tell software on your
computer that you want to use that proxy when communicating with other systems on the
Some Internet applications don't ordinarily work with a proxy because their developers didn't
create them with proxy support. However, many of these applications can be made to work with
a SOCKS proxy using socksifier software. Some examples of such software include:
tsocks ( on Unix/Linux
WideCap ( on Windows
ProxyCap ( on Windows
In most cases configuring applications to use a SOCKS proxy is done in much the same way as
configuring them to use HTTP proxies. Applications that support SOCKS proxies will have a
separate entry in the menu or configuration dialog where HTTP proxies are configured which let
you configure a SOCKS proxy. Some applications will ask you to choose between SOCKS 4 and
SOCKS 5 proxy settings; in most cases SOCKS 5 is the better option, although some SOCKS
proxies may only work with SOCKS 4.
Some applications, such as Mozilla Firefox, will allow you to configure both an HTTP proxy and a
SOCKS proxy at the same time. In this case, normal web-browsing will happen through the HTTP
proxy, and Firefox may use the SOCKS proxy for other traffic such as streaming video.
Mozilla Firefox
To configure Mozilla Firefox to use a SOCKS proxy:
1. Select Tools > Options:
2. The Options window appears:
3. In the toolbar at the top of the window, click Advanced:
4. Click the Network tab:
5. Click Settings. The Connection Settings window opens:
6. Select "Manual proxy configuration". The fields below that option become available.
7. Enter the SOCKS proxy address and port number, choose SOCKS v5, then click OK.
Now Firefox is configured to use a SOCKS proxy.
Microsoft Internet Explorer
To configure Internet Explorer to use a SOCKS proxy:
1. Select Tools > Internet Options:
2. Internet Explorer displays the Internet Options window:
3. Click the Connections tab:
4. Click LAN Settings. Internet Explorer displays the Local Area Network (LAN) Settings
5. Select "Use a proxy server for your LAN" and click Advanced.
Internet Explorer displays the Proxy Settings window:
6. Clear "Use the same proxy server for all protocols" if it is selected:
7. Enter the proxy address to use and port number in the Socks row and click OK:
Now Internet Explorer is configured to use a SOCKS proxy.
Configuring a SOCKS proxy for other applications
Many Internet applications other than Web browsers can use a SOCKS proxy to connect to the
Internet, potentially bypassing blocking. Here is an example with the instant messaging software
Pidgin. This is a typical example, but the exact sequence of steps to configure some other
application to use a SOCKS proxy would be slightly different.
1. Select Tools > Preferences:
2. Pidgin displays the Preferences window:
3. Click the Network tab:
4. For Proxy type, select SOCKS 5. Additional fields appear under that option.
5. Enter the host address and port number of your SOCKS proxy:
6. Click Close.
Pidgin is now configured to use a SOCKS proxy.
When you're done with the proxy
When you are done using a proxy, particularly on a shared computer, return the settings you've
changed to their previous values. Otherwise, those applications will continue to try to use the
proxy. This could be a problem if you don't want people to know that you were using the proxy
or if you were using a local proxy provided by a particular circumvention application that isn't
running all the time.
One important problem with SOCKS proxies is that some applications that support the use of
SOCKS proxies may not use the proxy for all their network communications. The most common
problem is that Domain Name System (DNS) requests may be made without going through the
proxy. This DNS leak can be a privacy problem and can also leave you vulnerable to DNS
blocking, which a proxy could otherwise have circumvented. Whether an application is vulnerable
to DNS leaks may vary from version to version. Mozilla Firefox is currently vulnerable to DNS
leaks in its default configuration, but you can avoid these by making a permanent configuration
change to prevent DNS leaks:
1. In the Firefox address bar, enter about:config as if it were a URL (you may see a warning
about changing advanced settings):
2. If necessary, click "I'll be careful, I promise!" to confirm that you want to modify your
browser settings. The browser displays a list of configuration settings information.
3. In the Filter field, enter network.proxy.socks_remote_dns. Only that setting is displayed:
4. If this setting has the value false, double-click it to change its value to true.
Firefox is now configured to avoid DNS leaks. Once the value is displayed as true, this setting is
automatically saved permanently.
There is no documented way to prevent DNS leaks within Microsoft Internet Explorer, without
using an external program.
At the time of this writing there are no known DNS leaks in Pidgin when configured to use a
SOCKS 5 proxy.
33. Researching and Documenting Censorship
34. Dealing with Port Blocking
35. Installing Web Proxies
36. Setting up a Tor Relay
37. Risks of Operating a Proxy
38. Best Practices for Webmasters
In many countries, it is no secret that government censorship of the Internet exists. The scope
and methods of censorship have been documented for example in the books Access Denied: The
Practice and Policy of Global Internet Filtering and Access Controlled: The Shaping of Power, Rights,
and Rule in Cyberspace, both edited by Ronald Delbert, John Palfrey, Rafal Rohozinski, and
Jonathan Zittrain ( and
When a popular site is widely blocked, that fact tends to become widely known within the
country. However, some governments (including some rather active censors) officially deny the
existence of censorship or try to disguise it as random technical errors. If you're subject to
censorship, you can use your situation to help others (including the international academic and
activist community that studies censorship) understand it and potentially publicize it.
Of course, you need to be cautious about this; governments that deny their network censorship
practice may not appreciate your participation in efforts to expose them.
Some censorship knowledge databases have been made public in the last couple of years. Some
of them are crowd-sourced but they are all validated by field experts. They are being constantly
updated to keep information and blocked sites lists as accurate as possible. Some databases are
available at the following URLs:
Herdict Web:
Alkasir Map:
On a more macro-geographic level, OpenNet Initiative and Reporters without Borders release a
"State of Internet" for every country on a regular basis. You can access them online:
OpenNet Initiative research report:
Reporters Without Borders Internet Enemies:
Herdict ( is a Web site which aggregates reports of inaccessible sites. It's
run by researchers at the Berkman Center For Internet and Society at Harvard University in the
United States who study how the Internet is being censored.
The data in Herdict isn't perfect – for example, many users can't distinguish a site that is not
available because of a technical glitch or because they mistyped the address from actual
censorship – but the data is collected from all over the world and is constantly updated.
Above is an overview of the Facebook report.
You can help these researchers by submitting your own reports to Herdict through their web
site. It is free, easy to use and you don't even have to register. You can also register to get
updates on future block notifications about a website.
Herdict also offers add-ons for the Firefox and Internet Explorer Web browsers to make it easier
to report whether particular Web sites are blocked or not as you browse the web.
Alkasir is a censorship circumvention tool with a build in research part which allows its users to
report a blocked Web site with a simple click on the "Report Blocked URLs" button. Alkasir
maintains a relevant list of blocked sites per country and may automatically check other related
URLs for availability. By using the report feature you can easily contribute to this research.
You can find more details about how to use the tool in the chapter "Using Alkasir".
You can also help censorship research by giving researchers remote access to your computer so
that they can use it to carry out their own tests. You should only do this if you trust the
researchers in question with the kind of access you're offering them, since they may get full
control over your computer and everything they do on your machine will look like your own
actions to your ISP or government.
For GNU/Linux operating systems a shell account is the best option; you can find help in setting
this up at and other sites.
For Windows operating systems the build-in remote desktop feature should be used. You can find
instructions for this at You may also have to change port forwarding settings on the router
box you use to connect to the Internet; this is explained on
Another solution for remote access is the free tool TeamViewer (
which is available for all operating systems.
The basic technique for documenting network censorship is to try to access a huge number of
network resources, such as a long list of URLs, from various places on the Internet and then
compare the results. Did some of the URLs fail to load in one place but not in another? Are
these differences ongoing and systematic? If you have a reliable circumvention technology such
as a VPN, you can do some of these experiments by yourself, by comparing how the net looks
with and without circumvention. For example, in the United States, this was the method used to
document how ISPs were disrupting the use of peer-to-peer filesharing software.
These comparisons can be done with automated software or by hand.
If you become familiar with the technical details of how Internet protocols work, a packet sniffer
like Wireshark ( will let you record the actual network packets that
your computer transmits and receives.
Network firewalls can be used to block all communications that are directed to a particular port
number. This can be used to try to prevent the use of a particular protocol or kind of network
software. To try to circumvent these restrictions, ISPs and users could arrange access to
services at non standard port numbers. This allows software to circumvent simple port blocking.
Many software applications can easily be made to use non standard port numbers. URLs for web
pages have a particularly convenient way of doing this right inside the URL. For example, the URL would tell a web browser to make an HTTP request to on port 8000, rather than the default http port 80. Of course, this will only work if
the web server software on is already expecting requests on port 8000.
You can test which ports (if any) are blocked on your connection using Telnet. Just open a
command line, type "telnet 5555" or "telnet 5555" and press
Enter. The number is the port you want to test. If you get some strange symbols in return, the
connection succeeded.
If, on the other hand, the computer reports that the connection failed, timed out, or was
interrupted, disconnected, or reset, that port is probably being blocked. (Keep in mind that some
ports could be blocked only in conjunction with certain IP addresses.)
If you have access to a Web server in a country which is not censoring access to the Internet,
you can install a Web proxy, which is a small software written in the programming languages
PHP, Perl, Python or ASP. Installation of Web-based circumvention software requires some
technical expertise and resources (a compatible Web hosting and sufficient bandwidth).
If you want to install your own Web proxy, you need one of the following:
a Web hosting space with PHP support (which can be purchased for a few US dollars a year
from hosting companies such as or,
or provided by your school or university)
a virtual (VPS) or dedicated server (which are more expensive and more complicated to
a PC connected to a broadband connection (with a publicly routable IP address).
Public Web proxies are available to anyone able to search them, on search engines such as
Google for example. Public Web proxies and anonymity services may be found by users and
those authorities implementing filtering, so they are more vulnerable to blacklisting.
The locations of Private Web proxies are only known to the intended users. Therefore, private
Web proxies are best suited for users who require stable circumvention services for Web traffic
and have trusted contacts in non-filtered locations with sufficient technical skills and available
bandwidth to set up and maintain the Web proxy. The chances of private Web proxies being
detected and blocked are lower than those of public circumvention services. This is also the
most flexible circumvention option available for simple Web traffic and is less likely to be
discovered and blocked than a public Web proxy, particularly if it is used with SSL encryption.
Web proxies can be set up with some level of customization tailored to the specific needs of the
end user. Common customizations would include changing the port number that the Web server
runs on and implementing encryption such as SSL. Since some blacklists may block keywords
associated with popular proxy software, changing items like the default URL, the name of the
script, or elements of the user interface can also reduce the risk of automated detection and
blocking of the proxy. It is possible to protect the use of the Web proxy by enabling .htaccess
with a username and a password.
When using SSL, it's also useful to create an innocuous Web page at the root of the Web server
and conceal the Web proxy with a random path and file name. Although intermediaries may be
able to determine the server you are connecting to, they will not be able to determine the
requested path because that part of the request is encrypted. For example, if a user connects
to, an intermediary will be able to determine that the user
connected to but they will not know that the user requested the Web proxy. If the
Web proxy operator places an innocuous page at, then the Web proxy is less likely
to be discovered by monitoring network transmissions. A valid SSL certificate which is trusted in
all popular Web browsers is available for free at
There are several free open source Web proxies available on the Internet. The main differences
are the programming languages they are written in, since not every Web server supports every
programming language. The other big difference is the compatibility of the script with modern
Web sites with technologies like AJAX (used by GMail or Facebook) or streaming Flash video (used
by YouTube).
Popular free Web proxy programs include:
CGIProxy ( a CGI script written in the Perl
programming language that acts as both an HTTP and an FTP proxy.
Peacefire's Circumventor ( an automated installer program that makes it much easier for nontechnical users to install and configure CGIProxy on a Windows machine.
SabzProxy ( both an HTTP and an FTP proxy. It is based on the
legacy code of PHProxy written in PHP with new features, such as random encoding of the
URL, to make it harder to block.
Glype Proxy ( another free-to-use, web-based proxy script, also
written in PHP.
The sites of these Web proxies provide instructions on how to set them up. Basically, this
involves downloading the script, extracting it on the local hard disk, uploading the script via FTP
or SCP to your Web server, setting permissions and testing the script. The following example is
for the installation of SabzProxy, but the steps are similar for other Web proxies.
SabzProxy is only available in Persian, but the GUI is simple and is still easy to understand.
These instructions describe the most common case: using FTP to transfer SabzProxy to a Web
space account that already supports PHP. For this technique, you will also need an FTP client
program such as FileZilla (
Although this method is the most common, it isn't applicable to every situation (for example if
you're setting up your own server through the comand line), but the steps should be similar.
1. The first step is to download the SabzProxy archive file from
2. Next, extract the contents of the .zip file by clicking with the right mouse button on the
file and choosing Extract All.
3. Open the config.php file with a basic text editor (e.g. Notepad for Windows, Gedit or Nano
for Linux systems, Texteditor for MacOS)
4. Edit line 8, starting with $config_key. Type a random string between "". This string will be
used to randomize the URL encoding, so make it as random as possible.
5. You can also configure a couple of options, such as the welcoming text and links.
6. Open FileZilla, enter the server (host), username and password of your Web space and
click on Quickconnect (or similar if you are using a different FTP client).
7. The left part of the FTP client window represents your local PC, so you can locate the
SabzProxy files that you have just extracted here.
8. Drag-and-drop the files from the left part of the FTP client window to the right part, which
represents the remote FTP server (your Web space).
9. You can now access SabzProxy by browsing to the domain of your Web space and the
directory to which you uploaded PHProxy. (In this example
If this doesn't work, your server account may not support PHP, or support for PHP may be
disabled or may require additional steps. Please refer to the documentation for your account or
the Web server software in use. You can also look for an appropriate support forum or ask your
web server operator for additional help.
If you live in an area with little or no Internet censorship, you may want to run a Tor relay or a
Tor bridge relay to help other Tor users access an uncensored Internet.
The Tor network relies on volunteers to donate bandwidth. The more people run relays, the
faster and more secure the Tor network will be. To help people using Tor bypass Internet
censorship, set up a bridge relay rather than an ordinary relay.
Bridge relays (or bridges for short) are Tor relays that are not listed in the main (and public) Tor
directory. Even if an ISP is filtering connections to all the known Tor relays, it probably will not be
able to block all the bridges.
A Tor node is a kind of public proxy, so running one can have the general risks of running a proxy
mentioned in the "Risks of Operating a Proxy" chapter of this manual. However, a Tor node is
typically set up in one of two ways: as an exit node or as a middleman node (sometimes
called a non-exit node). A middleman node forwards encrypted traffic only to other Tor nodes,
and does not allow anonymous users to communicate directly with sites outside of the Tor
network. Running either kind of node is helpful to the Tor network as a whole. Running an exit
node is particularly helpful because exit nodes are comparatively scarce. Running a middleman
node is comparatively less risky because the middleman node is unlikely to draw the kinds of
complaints that a public proxy might, since the IP address of a middleman node will never appear
on log files.
Since a bridge is not an exit node, you are unlikely to receive complaints about the use of a
bridge node by others.
Even though it is unlikely to draw specific complaints, operating a middleman or bridge node may
cause your ISP to object for more general reasons. For example, the ISP may disapprove of the
Tor network or may forbid subscribers from operating any sort of public service. You can find
more best practices on how to safety run a Tor exit node on
There are only a few prerequisites for running a Tor relay:
Your Internet connection needs to have a bandwidth of at least 20 kilobytes/second in
both directions (and it needs to be OK for your connection to be constantly in use when
your computer is on).
You need an Internet connection with an IP address that is publicly routable.
If your computer is behind a network address translation (NAT) firewall and doesn't have
access to its public (or external) IP address, you'll need to set up a port forwarding rule on
your router. You can do this via the Tor Universal Plug and Play facility, or manually, by
following the instructions in your router manual or at
What is not required:
Your computer does not have to be always on and online (the Tor directory will figure out
when it is).
You do not need to have a static IP address.
To download Tor, go to the Web site and click Download in the
navigation menu.
On the Available Tor Bundles page, select the stable version that fits your operating system.
You can find detailed instructions on how to set up a Tor relay or bridge on
Launch the installer and click Next when asked.
If you are using Firefox, install all the components proposed in the dialog shown below:
If you do not have Firefox installed, deselect Torbutton (you will have the option to install Firefox
and Torbutton afterwards).
When the installation is completed, launch Tor by clicking Finish with the "Run installed
components now" box selected, as in the dialog shown below:
To activate your bridge:
1. Open the Vidalia control panel.
2. In the Vidalia control panel, click Settings:
3. In the Settings window, click Sharing:
4. To create the bridge, click "Help censored users reach the Tor network":
5. If you are using a NAT IP address on a local network, you will need to create a port
forwarding rule in your router. You can ask Tor to try to configure port forwarding for you.
To do so, click "Attempt to automatically configure port forwarding":
6. Click Test to see if Tor has correctly created a setting for port forwarding in the router:
If Tor could not configure port forwarding, please read the Tor FAQ entry on this
Congratulations. If all has gone well, your bridge is up and running. Your bridge information will be
added to the hidden bridge directory and made available to users who request it.
If you specifically established your bridge to help a friend access the Tor network, you can copy
the information at the bottom of the Settings window and send it to her:
When you run a Web proxy or application proxy on your computer to help others, requests and
connections forwarded through that proxy will appear to originate from your computer. Your
computer is acting on behalf of other Internet users, so their activity could be attributed to you,
as if you had done it yourself. So if someone uses the proxy to send or receive material that a
third party objects to, you could receive complaints that assume that you are responsible and
may ask you to stop that activity. In some cases, activities using your proxy could attract legal
action or the attention of law enforcement agencies in your own or another country.
In some countries, proxy operators have received legal complaints, and, in some cases, law
enforcement agents have even seized computers that were functioning as proxies. This could
happen for several reasons:
Someone may (incorrectly) assume that the operator of the proxy computer was
personally involved in activity passing through the proxy.
Someone may assert that the operator of the proxy has a legal duty to stop certain uses,
even if the uses are being made by third parties.
Someone may hope to examine the proxy to find evidence (e.g. logfiles) of who was
responsible for some activity.
If you think this could be a risk for your proxy in your area, it may be safer to operate the proxy
on a dedicated computer in a data center. That way it won't attract attention to your home
Internet connection.
National laws may vary in the way and extent they protect proxy operators from liability. For
details about your situation, you should consult a lawyer or qualified legal expert in your
Internet service providers may complain about your operation of a proxy, especially if they
receive complaints about abuse of the proxy. Some ISPs may assert that running a public proxy
violates their terms of service, or that they simply do not wish to permit users to run public
proxies. These ISPs may disconnect you or threaten to disconnect you in the future.
A public proxy may be used by many people all over the world and may use huge amounts of
bandwidth and traffic, so when using ISPs that charge on a non-flat-rate tariff, one should take
precautions to avoid a large traffic bill at the end of the month.
These risks still exist if you operate a proxy for your own benefit or for the use of a small
number of individuals, but operating a non-public proxy is much less risky than operating a public
If the user of your non-public proxy is detected and monitored, whoever is doing the monitoring
may realize or speculate that there is a connection between you and the user and that you are
trying to help that person circumvent filtering.
Although your own ISP is much more likely to object to your running a public proxy than a private
proxy, some ISPs may have such comprehensive anti-proxy policies that they object even to the
operation of a private proxy on their networks.
In some countries, data retention laws or similar laws meant to restrict anonymity might be
interpreted to regulate the operation of proxy services. For more information about data
retention, see
Running a Web site, exposed to a wide audience or not, is not always easy. It is important to
think about your personal safety as well as the safety of the visitors. Often, Webmasters are
surprised when their Web sites are unexpectedly blocked in a certain country. If a large number
of visitors are unable to access the site, the site operator may also face economic problems.
Losing your Web site content or server, or having to set up a new server can also be disturbing
and frustrating.
This chapter intends to gather a checklist of good practices and advice to have in mind when
running your Web site.
Always schedule automated backups (files and database) on at least one another
physical machine. Be sure to know how to restore it.
Monitor your traffic to learn something about the countries your visitors come from. You
can use geo location databases to make a guess about which country an IP address is
located in. If you notice a major drop in traffic from a specific country, your Web site may
have been blocked. You can share this with geographical blocked Web sites databases, like
Herdict (
Secure your Web site, especially if you use a CMS (Content Management System). Always
install the latest stable updates to fix security flaws.
Secure your Web server software with high level security settings (you can find plenty
of online resources about how to secure Linux Web servers).
Register (or transfer) your domain name to another DNS provider which is not your
hosting provider. In case of attack on your current provider, you will be able to easily point
your domain name to a new hosting provider.
You may also want to create a mirror server running as a standby to which you can
switch easily. Learn how to switch your DNS entries to the mirror server.
Consider hosting your website in a foreign country, where the content is less
controversial and clearly legally protected. This may imply only a small additional delay in
page load time (usually a few milliseconds) for your visitors and may save you a lot of
trouble if you are located in a country where you web site's content is considered very
Test and optimize your website with the main circumvention tools your visitors are
likely to use. Check and fix any broken pages or features. Ideally, make your website
usable to visitors without JavaScript or plugins, since these may be unavailable or broken
when people are using proxies.
Avoid using FTP to upload your files. FTP sends your password over the Internet
unencrypted, making it easy for eavesdroppers to steal your login credentials. Consider
using SFTP (File Transfer Protocol over SSH), SCP, or secure WebDAV (over HTTPS) instead.
Use alternative ports to access your back-end. Hackers usually run automatic scans on
standard ports to detect vulnerabilities. Consider changing your ports to non-standard
values (such as SSH) to minimize the risks of these attacks.
Protect your server against brute-force attacks by installing a tool such as DenyHosts
on your server ( to protect your server by blacklisting IPs
that attempt unsuccessful logins more than a certain amount of times.
Here are some tips to prevent potential personal harm, if staying anonymous as a webmaster is
important for you.
Use an anonymous e-mail address and name which is never associated with your real
If you own a dedicated domain name, you can record dummy entries in the WHOIS public
database by using a service often called "WHOIS proxy", "WHOIS protect" or "domain
Use a service like Tor to stay anonymous when updating your Web site.
Apart from protecting your Web site and yourself, it is also important to protect the visitors
from potential third party monitoring, especially if they submit content to your website.
Deploy HTTPS so your users can access your site over an encrypted connection, to make
it more difficult to look automatically at the content which is being transferred and to
assure your identity. Ensure that your HTTPS configuration covers your entire site and
that you use other best practices for HTTPS configuration. You can find information on
how to deploy it correctly on and also
try the automated tests at for many technical parameters.
Minimize retained data in your logs. Avoid saving IP addresses or any personal data
related to your visitors longer than necessary.
Encrypt critical user data such as passwords, for example using salted hashes.
External services like Google Analytics or other third-party content like ad networks are
difficult to control. Avoid them.
Create a light and secure version of your Web site, without any Flash or Javascript
embedded code, compliant with Tor and low-bandwidth connections.
Teach your users how to use circumvention tools, and be able to improve their online
Make a digital safety checklist available so your visitors can be sure they are not being
monitored or attacked.
Host Web proxy instances (such as SabzProxy or Glype Proxy). Share them with your
visitors, by email, through your social networks.
Send out psiphon invitations if you have an account on a private node
Install other kinds of Web and application proxies if you own a dedicated server and
share it.
Link to this manual or relevant circumvention tools from your website.
Webmasters can and should take different actions in order to spread their content as much as
possible, to prevent being shut down or blocked.
Set up a newsletter, and send regular updates of new content by e-mail. You will still be
able to reach users when they are not able to visit your Web site anymore.
Set up a RSS feed and make sure it contains full articles and not only excerpts (snippets).
This way your content can be parsed very easily by third party websites and applications
such as Google Reader, which can be used to read your content where direct access is
Share your content on popular social networking platforms, such as Facebook or
Twitter, which may be hard to block.
Spread the content as much as possible. Make your content available for download.
Wikipedia, for example distributes its entire content freely as a database dump which can
used to easily create new mirror Web sites with the same content elsewhere.
Consider publishing your articles under an open license (like GPL or Creative
Commons) which allows everyone to reuse your content and create mirrors.
Mirror your files on free sharehosting services like or
and peer-to-peer filesharing software like Bittorrent.
Configure your Web server to also serve content on different ports than the standard
ports 80 (http) and 443 (https).
Offer an API (application programming interface) which allows others to access your
content automatically via third-party software such as Twitter or Wikipedia does.
Reducing your page load time not only will save you some bandwidth and money, but will also
help your visitors coming from developing countries to access your information better. A good
list of best practices for speeding up your website can be found at and
Adopt a minimalist style. Consider keeping images to a minimum, and use CSS to style
your layout. A good introduction to CSS can be found at
Optimize your images. Use programs like OptiPNG ( to
make your pictures load faster by optimizing them for the Web. Also, never scale images
with HTML if you don't need to (i.e. if you need a 60x60 image then resize it directly,
rather than using HTML).
Reduce Java, JavaScript, Flash and other content that runs in the client's computer to a
minimum. Remember that some Internet cafés disable this kind of content for security
reasons. Make sure that the information you want to convey is displayed in pure HTML.
Use external files for your CSS and JavaScript. If you have a certain CSS style or
JavaScript that is recurrent in your Web site, consider saving it in a separate file and calling
it in the header of your Web page. This will allow your client's browser to cache the files,
and they will not have to download all this content each time they visit a Web page on
your site.
Minify your code. Remove any unnecessary break lines and spaces. Some tools that do
this automatically can be found at
Reduce the number of server requests to a minimum. If you have a dynamic Web site
but the content doesn't change really frequently, you may want to install some cache
extensions that will provide your users with a static version of your content, thus
significantly reducing the number of requests to your database.
39. Glossary
40. Ten things
41. Further Resources
42. License
Much of this content is based on
An aggregator is a service that gathers syndicated information from one or many sites and
makes it available at a different address. Sometimes called an RSS aggregator, a feed
aggregator, a feed reader, or a news reader. (Not to be confused with a Usenet News reader.)
(Not be confused with privacy, pseudonymity, security, or confidentiality.)
Anonymity on the Internet is the ability to use services without leaving clues to one's identity.
The level of protection depends on the anonymity techniques used and the extent of monitoring.
The strongest techniques in use to protect anonymity involve creating a chain of communication
using a random process to select some of the links, in which each link has access to only partial
information about the process. The first knows the user's IP address but not the content,
destination, or purpose of the communication, because the message contents and destination
information are encrypted. The last knows the identity of the site being contacted, but not the
source of the session. One or more steps in between prevents the first and last links from
sharing their partial knowledge in order to connect the user and the target site.
An anonymous remailer is a service that accepts e-mail messages containing instructions for
delivery, and sends them out without revealing their sources. Since the remailer has access to
the user's address, the content of the message, and the destination of the message, remailers
should be used as part of a chain of multiple remailers so that no one remailer knows all this
An ASP is an organization that offers software services over the Internet, allowing the software
to be upgraded and maintained centrally.
A backbone is one of the high-bandwidth communications links that tie together networks in
different countries and organizations around the world to form the Internet.
See malware.
The bandwidth of a connection is the maximum rate of data transfer on that connection, limited
by its capacity and the capabilities of the computers at both ends of the connection.
The bash shell is a command-line interface for Linux/Unix operating systems, based on the
Bourne shell.
BitTorrent is a peer-to-peer file-sharing protocol invented by Bram Cohen in 2001. It allows
individuals to cheaply and effectively distribute large files, such as CD images, video, or music
A blacklist is a list of forbidden persons or things. In Internet censorship, lists of forbidden Web
sites may be used as blacklists; censorware may allow access to all sites except for those
specifically listed on its blacklist. An alternative to a blacklist is a whitelist, or a list of permitted
things. A whitelist system blocks access to all sites except for those specifically listed on the
whitelist. This is a less common approach to Internet censorship. It is possible to combine both
approaches, using string matching or other conditional techniques on URLs that do not match
either list.
The blue URL bar (called the Bluebar in Psiphon lingo) is the form at the top of your Psiphon node
browser window, which allows you to access blocked site by typing its URL inside.
See also Psiphon node
To block is to prevent access to an Internet resource, using any number of methods.
A bookmark is a placeholder within software that contains a reference to an external resource.
In a browser, a bookmark is a reference to a Web page – by choosing the bookmark you can
quickly load the Web site without needing to type in the full URL.
See Tor bridge.
A brute force attack consists of trying every possible code, combination, or password until you
find the right one. These are some of the most trivial hacking attacks.
A cache is a part of an information-processing system used to store recently used or frequently
used data to speed up repeated access to it. A Web cache holds copies of Web page files.
To censor is to prevent publication or retrieval of information, or take action, legal or otherwise,
against publishers and readers.
Censorware is software used to filter or block access to the Internet. This term is most often
used to refer to Internet filtering or blocking software installed on the client machine (the PC
which is used to access the Internet). Most such client-side censorware is used for parental
control purposes.
Sometimes the term censorware is also used to refer to software used for the same purpose
installed on a network server or router.
CGI is a common standard used to let programs on a Web server run as Web applications. Many
Web-based proxies use CGI and thus are also called "CGI proxies". (One popular CGI proxy
application written by James Marshall using the Perl programming language is called CGIProxy.)
Chat, also called instant messaging, is a common method of communication among two or
more people in which each line typed by a participant in a session is echoed to all of the others.
There are numerous chat protocols, including those created by specific companies (AOL, Yahoo!,
Microsoft, Google, and others) and publicly defined protocols. Some chat client software uses only
one of these protocols, while others use a range of popular protocols.
Circumvention is publishing or accessing content in spite of attempts at censorship.
See CGI.
A method of controlling the execution of software using commands entered on a keyboard, such
as a Unix shell or the Windows command line.
A cookie is a text string sent by a Web server to the user's browser to store on the user's
computer, containing information needed to maintain continuity in sessions across multiple Web
pages, or across multiple sessions. Some Web sites cannot be used without accepting and storing
a cookie. Some people consider this an invasion of privacy or a security risk.
Each country has a two-letter country code, and a TLD (top-level domain) based on it, such as
.ca for Canada; this domain is called a country code top-level domain. Each such ccTLD has a
DNS server that lists all second-level domains within the TLD. The Internet root servers point to
all TLDs, and cache frequently-used information on lower-level domains.
DARPA is the successor to ARPA, which funded the Internet and its predecessor, the ARPAnet.
Decryption is recovering plain text or other messages from encrypted data with the use of a
See also encryption.
A domain can be a Top-Level Domain (TLD) or secondary domain on the Internet.
See also Top-Level Domain, country code Top-Level Domain and secondary domain.
The Domain Name System (DNS) converts domain names, made up of easy-to-remember
combinations of letters, to IP addresses, which are hard-to-remember strings of numbers. Every
computer on the Internet has a unique address (a little bit like an area code+telephone number).
A DNS leak occurs when a computer configured to use a proxy for its Internet connection
nonetheless makes DNS queries without using the proxy, thus exposing the user's attempts to
connect with blocked sites. Some Web browsers have configuration options to force the use of
the proxy.
A DNS server, or name server, is a server that provides the look-up function of the Domain
Name System. It does this either by accessing an existing cached record of the IP address of a
specific domain, or by sending a request for information to another name server.
A DNS tunnel is a way to tunnel almost everything over DNS/Nameservers.
Because you "abuse" the DNS system for an unintended purpose, it only allows a very slow
connection of about 3 kb/s which is even less than the speed of an analog modem. That is not
enough for YouTube or file sharing, but should be sufficient for instant messengers like ICQ or
MSN Messenger and also for plain text e-mail.
On the connection you want to use a DNS tunnel, you only need port 53 to be open; therefore it
even works on many commercial Wi-Fi providers without the need to pay.
The main problem is that there are no public modified nameservers that you can use. You have
to set up your own. You need a server with a permanent connection to the Internet running
Linux. There you can install the free software OzymanDNS and in combination with SSH and a
proxy like Squid you can use the tunnel. More Information on this on
Eavesdropping is listening to voice traffic or reading or filtering data traffic on a telephone line or
digital data connection, usually to detect or prevent illegal or unwanted activities or to control or
monitor what people are talking about.
E-mail, short for electronic mail, is a method to send and receive messages over the Internet. It
is possible to use a Web mail service or to send e-mails with the SMTP protocol and receive
them with the POP3 protocol by using an e-mail client such as Outlook Express or Thunderbird. It
is comparatively rare for a government to block e-mail, but e-mail surveillance is common. If email is not encrypted, it could be read easily by a network operator or government.
An embedded script is a piece of software code.
Encryption is any method for recoding and scrambling data or transforming it mathematically to
make it unreadable to a third party who doesn't know the secret key to decrypt it. It is possible
to encrypt data on your local hard drive using software like TrueCrypt (
or to encrypt Internet traffic with SSL or SSH.
See also decryption.
An exit node is a Tor node that forwards data outside the Tor network.
See also middleman node.
File sharing refers to any computer system where multiple people can use the same information,
but often refers to making music, films or other materials available to others free of charge over
the Internet.
A file spreading engine is a Web site a publisher can use to get around censorship. A user only
has to upload a file to publish once and the file spreading engine uploads that file to some set of
sharehosting services (like Rapidshare or Megaupload).
To filter is to search in various ways for specific data patterns to block or permit
Firefox is the most popular free and open source Web browser, developed by the Mozilla
On a Web site, a forum is a place for discussion, where users can post messages and comment
on previously posted messages. It is distinguished from a mailing list or a Usenet newsgroup by
the persistence of the pages containing the message threads. Newsgroup and mailing list
archives, in contrast, typically display messages one per page, with navigation pages listing only
the headers of the messages in a thread.
A frame is a portion of a Web page with its own separate URL. For example, frames are
frequently used to place a static menu next to a scrolling text window.
The FTP protocol is used for file transfers. Many people use it mostly for downloads; it can also
be used to upload Web pages and scripts to some Web servers. It normally uses ports 20 and 21,
which are sometimes blocked. Some FTP servers listen to an uncommon port, which can evade
port-based blocking.
A popular free and open source FTP client for Windows and Mac OS is FileZilla. There are also
some Web-based FTP clients that you can use with a normal Web browser like Firefox.
A gateway is a node connecting two networks on the Internet. An important example is a
national gateway that requires all incoming or outgoing traffic to go through it.
A honeypot is a site that pretends to offer a service in order to entice potential users to use it,
and to capture information about them or their activities.
A hop is a link in a chain of packet transfers from one computer to another, or any computer
along the route. The number of hops between computers can give a rough measure of the delay
(latency) in communications between them. Each individual hop is also an entity that has the
ability to eavesdrop on, block, or tamper with communications.
HTTP is the fundamental protocol of the World Wide Web, providing methods for requesting and
serving Web pages, querying and generating answers to queries, and accessing a wide range of
Secure HTTP is a protocol for secure communication using encrypted HTTP messages.
Messages between client and server are encrypted in both directions, using keys generated when
the connection is requested and exchanged securely. Source and destination IP addresses are in
the headers of every packet, so HTTPS cannot hide the fact of the communication, just the
contents of the data transmitted and received.
IANA is the organization responsible for technical work in managing the infrastructure of the
Internet, including assigning blocks of IP addresses for top-level domains and licensing domain
registrars for ccTLDs and for the generic TLDs, running the root name servers of the Internet,
and other duties.
ICANN is a corporation created by the US Department of Commerce to manage the highest
levels of the Internet. Its technical work is performed by IANA.
Instant messaging is either certain proprietary forms of chat using proprietary protocols, or chat
in general. Common instant messaging clients include MSN Messenger, ICQ, AIM or Yahoo!
See man in the middle.
The Internet is a network of networks interconnected using TCP/IP and other communication
An IP address is a number identifying a particular computer on the Internet. In the previous
version 4 of the Internet Protocol an IP address consisted of four bytes (32 bits), often
represented as four integers in the range 0-255 separated by dots, such as In IPv6,
which the Net is currently switching to, an IP address is four times longer, and consists of 16
bytes (128 bits). It can be written as 8 groups of 4 hex digits separated by colons, such as
IRC is a more than 20-year-old Internet protocol used for real-time text conversations (chat or
instant messaging). There exist several IRC networks -- the largest have more than 50 000
An ISP (Internet service provider) is a business or organization that provides access to the
Internet for its customers.
JavaScript is a scripting language, commonly used in Web pages to provide interactive functions.
A keyword filter scans all Internet traffic going through a server for forbidden words or terms to
Latency is a measure of time delay experienced in a system, here in a computer network. It is
measured by the time between the start of packet transmission to the start of packet reception,
between one network end (e.g. you) to the other end (e.g. the Web server). One very powerful
way of Web filtering is maintaining a very high latency, which makes lots of circumvention tools
very difficult to use.
A log file is a file that records a sequence of messages from a software process, which can be an
application or a component of the operating system. For example, Web servers or proxies may
keep log files containing records about which IP addresses used these services when and what
pages were accessed.
A low-bandwidth filter is a Web service that removes extraneous elements such as advertising
and images from a Web page and otherwise compresses it, making page download much quicker.
Malware is a general term for malicious software, including viruses, that may be installed or
executed without your knowledge. Malware may take control of your computer for purposes
such as sending spam. (Malware is also sometimes called badware.)
A man in the middle or man-in-the-middle is a person or computer capturing traffic on a
communication channel, especially to selectively change or block content in a way that
undermines cryptographic security. Generally the man-in-the-middle attack involves
impersonating a Web site, service, or individual in order to record or alter communications.
Governments can run man-in-the-middle attacks at country gateways where all traffic entering
or leaving the country must pass.
A middleman node is a Tor node that is not an exit node. Running a middleman node can be
safer than running an exit node because a middleman node will not show up in third parties' log
files. (A middleman node is sometimes called a non-exit node.)
To monitor is to check a data stream continuously for unwanted activity.
NAT is a router function for hiding an address space by remapping. All traffic going out from the
router then uses the router's IP address, and the router knows how to route incoming traffic to
the requestor. NAT is frequently implemented by firewalls. Because incoming connections are
normally forbidden by NAT, NAT makes it difficult to offer a service to the general public, such
as a Web site or public proxy. On a network where NAT is in use, offering such a service
requires some kind of firewall configuration or NAT traversal method.
A network operator is a person or organization who runs or controls a network and thus is in a
position to monitor, block, or alter communications passing through that network.
A node is an active device on a network. A router is an example of a node. In the Psiphon and
Tor networks, a server is referred to as a node.
See middleman node.
Obfuscation means obscuring text using easily-understood and easily-reversed transformation
techniques that will withstand casual inspection but not cryptanalysis, or making minor changes
in text strings to prevent simple matches. Web proxies often use obfuscation to hide certain
names and addresses from simple text filters that might be fooled by the obfuscation. As
another example, any domain name can optionally contain a final dot, as in "",
but some filters might search only for "" (without the final dot).
An open node is a specific Psiphon node which can be used without logging in. It automatically
loads a particular homepage, and presents itself in a particular language, but can then be used to
browse elsewhere.
See also Psiphon node.
A packet is a data structure defined by a communication protocol to contain specific
information in specific forms, together with arbitrary data to be communicated from one point to
another. Messages are broken into pieces that will fit in a packet for transmission, and
reassembled at the other end of the link.
A peer-to-peer (or P2P) network is a computer network between equal peers. Unlike clientserver networks there is no central server and so the traffic is distributed only among the
clients.This technology is mostly applied to file sharing programs like BitTorrent, eMule and
Gnutella. But also the very old Usenet technology or the VoIP program Skype can be
categorized as peer-to-peer systems.
See also file sharing.
PHP is a scripting language designed to create dynamic Web sites and web applications. It is
installed on a Web server. For example, the popular Web proxy PHProxy uses this technology.
Plain text is unformatted text consisting of a sequence of character codes, as in ASCII plain text
or Unicode plain text.
Plaintext is unencrypted text, or decrypted text.
See also encryption, SSL, SSH.
Protection of personal privacy means preventing disclosure of personal information without the
permission of the person concerned. In the context of circumvention, it means preventing
observers from finding out that a person has sought or received information that has been
blocked or is illegal in the country where that person is at the time.
Post Office Protocol version 3 is used to receive mail from a server, by default on port 110 with
an e-mail program such as Outlook Express or Thunderbird.
A hardware port on a computer is a physical connector for a specific purpose, using a particular
hardware protocol. Examples are a VGA display port or a USB connector.
Software ports also connect computers and other devices over networks using various protocols,
but they exist in software only as numbers. Ports are somewhat like numbered doors into
different rooms, each for a special service on a server or PC. They are identified by numbers
from 0 to 65535.
A formal definition of a method of communication, and the form of data to be transmitted to
accomplish it. Also, the purpose of such a method of communication. For example, Internet
Protocol (IP) for transmitting data packets on the Internet, or Hypertext Transfer Protocol for
interactions on the World Wide Web.
A proxy server is a server, a computer system or an application program which acts as a
gateway between a client and a Web server. A client connects to the proxy server to request a
Web page from a different server. Then the proxy server accesses the resource by connecting
to the specified server, and returns the information to the requesting site. Proxy servers can
serve many different purposes, including restricting Web access or helping users route around
A Psiphon node is a secured web proxy designed to evade Internet censorship. It is developed by
Psiphon inc. Psiphon nodes can be open or private.
A private node is a Psiphon node working with authentication, which means that you have to
register before you can use it. Once registered, you will be able to send invitations to your
friends and relatives to use this specific node.
See also Psiphon node.
Publicly routable IP addresses (sometimes called public IP addresses) are those reachable in the
normal way on the Internet, through a chain of routers. Some IP addresses are private, such as
the 192.168.x.x block, and many are unassigned.
A regular expression (also called a regexp or RE) is a text pattern that specifies a set of text
strings in a particular regular expression implementation such as the UNIX grep utility. A text
string "matches" a regular expression if the string conforms to the pattern, as defined by the
regular expression syntax. In each RE syntax, some characters have special meanings, to allow
one pattern to match multiple other strings. For example, the regular expression lo+se matches
lose , loose , and looose .
An anonymous remailer is a service which allows users to send e-mails anonymously. The
remailer receives messages via e-mail and forwards them to their intended recipient after
removing information that would identify the original sender. Some also provide an anonymous
return address that can be used to reply to the original sender without disclosing her identity.
Well-known Remailer services include Cypherpunk, Mixmaster and Nym.
A router is a computer that determines the route for forwarding packets. It uses address
information in the packet header and cached information on the server to match address
numbers with hardware connections.
A root name server or root server is any of thirteen server clusters run by IANA to direct
traffic to all of the TLDs, as the core of the DNS system.
RSS is a method and protocol for allowing Internet users to subscribe to content from a Web
page, and receive updates as soon as they are posted.
On the Web, a scheme is a mapping from a name to a protocol. Thus the HTTP scheme maps
URLs that begin with HTTP: to the Hypertext Transfer Protocol. The protocol determines the
interpretation of the rest of the URL, so that identifies
a Web site and a specific file in a specific directory, and mailto:[email protected] is an email address of a specific person or group at a specific domain.
A UNIX shell is the traditional command line user interface for the UNIX/Linux operating
systems. The most common shells are sh and bash.
A SOCKS proxy is a special kind of proxy server. In the ISO/OSI model it operates between the
application layer and the transport layer. The standard port for SOCKS proxies is 1080, but they
can also run on different ports. Many programs support a connection through a SOCKS proxy. If
not you can install a SOCKS client like FreeCap, ProxyCap or SocksCap which can force programs
to run through the Socks proxy using dynamic port forwarding. It is also possible to use SSH
tools such as OpenSSH as a SOCKS proxy server.
A screenlogger is software able to record everything your computer displays on the screen. The
main feature of a screenlogger is to capture the screen and log it into files to view at any time in
the future. Screen loggers can be used as powerful monitoring tool. You should be aware of any
screen logger running on any computer you are using, anytime.
A script is a program, usually written in an interpreted, non-compiled language such as
JavaScript, Java, or a command interpreter language such as bash. Many Web pages include
scripts to manage user interaction with a Web page, so that the server does not have to send a
new page for each change.
A smartphone is a mobile phone that offers more advanced computing ability and connectivity
than a contemporary feature phone, such as Web access, ability to run elaborated operating
systems and run built-in applications.
Spam is messages that overwhelm a communications channel used by people, most notably
commercial advertising sent to large numbers of individuals or discussion groups. Most spam
advertises products or services that are illegal in one or more ways, almost always including
fraud. Content filtering of e-mail to block spam, with the permission of the recipient, is almost
universally approved of.
SSH or Secure Shell is a network protocol that allows encrypted communication between
computers. It was invented as a successor of the unencrypted Telnet protocol and is also used
to access a shell on a remote server.
The standard SSH port is 22. It can be used to bypass Internet censorship with port forwarding
or it can be used to tunnel other programs like VNC.
SSL (or Secure Sockets Layer), is one of several cryptographic standards used to make Internet
transactions secure. It is was used as the basis for the creation of the related Transport Layer
Security (TLS). You can easily see if you are using SSL/TLS by looking at the URL in your
Browser (like Firefox or Internet Explorer): If it starts with https instead of http, your connection
is encrypted.
Steganography, from the Greek for hidden writing, refers to a variety of methods of sending
hidden messages where not only the content of the message is hidden but the very fact that
something covert is being sent is also concealed. Usually this is done by concealing something
within something else, like a picture or a text about something innocent or completely unrelated.
Unlike cryptography, where it is clear that a secret message is being transmitted, steganography
does not attract attention to the fact that someone is trying to conceal or encrypt a message.
A subdomain is part of a larger domain. If for example "" is the domain for the
Wikipedia, "" is the subdomain for the English version of the Wikipedia.
A security threat analysis is properly a detailed, formal study of all known ways of attacking the
security of servers or protocols, or of methods for using them for a particular purpose such as
circumvention. Threats can be technical, such as code-breaking or exploiting software bugs, or
social, such as stealing passwords or bribing someone who has special knowledge. Few companies
or individuals have the knowledge and skill to do a comprehensive threat analysis, but everybody
involved in circumvention has to make some estimate of the issues.
In Internet names, the TLD is the last component of the domain name. There are several
generic TLDs, most notably .com, .org, .edu, .net, .gov, .mil, .int, and one two-letter country code
(ccTLD) for each country in the system, such as .ca for Canada. The European Union also has
the two-letter code .eu.
TLS or Transport Layer Security is a cryptographic standard based on SSL, used to make
Internet transactions secure.
TCP and IP are the fundamental protocols of the Internet, handling packet transmission and
routing. There are a few alternative protocols that are used at this level of Internet structure,
such as UDP.
A bridge is a middleman Tor node that is not listed in the main public Tor directory, and so is
possibly useful in countries where the public relays are blocked. Unlike the case of exit nodes,
IP addresses of bridge nodes never appear in server log files and never pass through monitoring
nodes in a way that can be connected with circumvention.
Traffic analysis is statistical analysis of encrypted communications. In some circumstances
traffic analysis can reveal information about the people communicating and the information being
A tunnel is an alternate route from one computer to another, usually including a protocol that
specifies encryption of messages.
UDP is an alternate protocol used with IP. Most Internet services can be accessed using either
TCP or UDP, but there are some that are defined to use only one of these alternatives. UDP is
especially useful for real-time multimedia applications like Internet phone calls (VoIP).
The URL (Uniform Resource Locator) is the address of a Web site. For example, the URL for the
World News section of the NY Times is Many
censoring systems can block a single URL. Sometimes an easy way to bypass the block is to
obscure the URL. It is for example possible to add a dot after the site name, so the URL becomes If you are lucky with this little
trick you can access blocked Web sites.
Usenet is a more than 20-year-old discussion forum system accessed using the NNTP protocol.
The messages are not stored on one server but on many servers which distribute their content
constantly. Because of that it is impossible to censor Usenet as a whole, however access to
Usenet can and is often blocked, and any particular server is likely to carry only a subset of
locally-acceptable Usenet newsgroups. Google archives the entire available history of Usenet
messages for searching.
VoIP refers to any of several protocols for real-time two-way voice communication on the
Internet, which is usually much less expensive than calling over telephone company voice
networks. It is not subject to the kinds of wiretapping practiced on telephone networks, but can
be monitored using digital technology. Many companies produce software and equipment to
eavesdrop on VoIP calls; securely encrypted VoIP technologies have only recently begun to
A VPN (virtual private network) is a private communication network used by many companies
and organizations to connect securely over a public network. Usually on the Internet it is
encrypted and so nobody except the endpoints of the communication can look at the data
traffic. There are various standards like IPSec, SSL, TLS or PPTP. The use of a VPN provider is a
very fast secure and convenient method to bypass Internet censorship with little risks but it
generally costs money every month.
A whitelist is a list of sites specifically authorized for a particular form of communication. Filtering
traffic can be done either by a whitelist (block everything but the sites on the list), a blacklist
(allow everything but the sites on the list), a combination of the two, or by other policies based
on specific rules and conditions.
The World Wide Web is the network of hyperlinked domains and content pages accessible using
the Hypertext Transfer Protocol and its numerous extensions. The World Wide Web is the most
famous part of the Internet.
Webmail is e-mail service through a Web site. The service sends and receives mail messages for
users in the usual way, but provides a Web interface for reading and managing messages, as an
alternative to running a mail client such as Outlook Express or Thunderbird on the user's
computer. For example a popular and free webmail service is
A Web proxy is a script running on a Web server which acts as a proxy/gateway. Users can
access such a Web proxy with their normal Web browser (like Firefox) and enter any URL in the
form located on that Web site. Then the Web proxy program on the server receives that Web
content and displays it to the user. This way the ISP only sees a connection to the server with
the Web proxy since there is no direct connection.
WHOIS (who is) is the aptly named Internet function that allows one to query remote WHOIS
databases for domain registration information. By performing a simple WHOIS search you can
discover when and by whom a domain was registered, contact information, and more.
A WHOIS search can also reveal the name or network mapped to a numerical IP address
by Roger Dingledine, project leader for The Tor Project
As more countries crack down on Internet use, people around the world are turning to anticensorship software that lets them reach blocked websites. Many types of software, also known
as circumvention tools, have been created to answer the threat to freedom online. These tools
provide different features and levels of security, and it's important for users to understand the
This article lays out ten features you should consider when evaluating a circumvention tool. The
goal isn't to advocate for any specific tool, but to point out what kind of tools are useful for
different situations. I've chosen the order of features based on ease of presentation; so you
shouldn't conclude the first feature is the most critical.
Internet-based circumvention software consists of two components: a relaying component and a
discovery component. The relaying component is what establishes a connection to some server
or proxy, handles encryption, and sends traffic back and forth. The discovery component is the
step before that the process of finding one or more reachable addresses.
Some tools have a simple relaying component. For example, if you're using an open proxy, the
process of using the proxy is straightforward: you configure your web browser or other
application to use the proxy. The big challenge for open proxy users is finding an open proxy
that's reliable and fast. On the other hand, some tools have much more sophisticated relaying
components, made up of multiple proxies, multiple layers of encryption, and so on.
One caveat to start out: I'm an inventor and developer of a tool called Tor that is used both for
privacy and for circumvention. While my bias for more secure tools like Tor shows through here
based on which features I've picked (meaning I raise issues that highlight Tor's strengths and that
some other tool developers may not care about), I have also tried to include features that other
tool developers consider important.
1. Has a diverse set of users
One of the simplest questions you can ask when looking at a circumvention tool is who else uses
it. A wide variety of users means that if somebody finds out you are using the software, they
can't conclude much about why you're using it. A privacy tool like Tor has many different classes
of users around the world (ranging from ordinary people and human rights activists to
corporations, law enforcement, and militaries) so the fact that you have Tor installed doesn't
give people much additional information about who you are or what sorts of sites you might visit.
On the other hand, imagine a group of Iranian bloggers using a circumvention tool created just for
them. If anybody discovers that one of them is using it, they can easily guess why.
Beyond technical features that make a given tool useful to a few people in one country or people
all over the world, marketing plays a big role in which users show up. A lot of tools spread
through word of mouth, so if the first few users are in Vietnam and they find it useful, the next
users will tend to be from Vietnam too. Whether a tool is translated into some languages but not
others can also direct (or hamper) which users it will attract.
2. Works in your country
The next question to consider is whether the tool operator artificially restricts which countries
can use it. For several years, the commercial made its service free to people in
Iran. Thus connections coming from Anonymizer's servers were either paying customers (mostly
in America) or people in Iran trying to get around their country's filters.
For more recent examples,
Your-Freedom restricts free usage to a few countries such as Burma, while at times systems
like Freegate and UltraSurf outright block connections from all but the few countries that they
care to serve (China and, in the case of Ultrasurf recently, Iran). On the one hand, this strategy
makes sense in terms of limiting the bandwidth costs. But on the other hand, if you're in Saudi
Arabia and need a circumvention tool, some otherwise useful tools are not an option for you.
3. Has a sustainable network and software development strategy
If you're going to invest the time to figure out how to use a given tool, you want to make sure
it's going to be around for a while. There are several ways that different tools ensure their longterm existence. The main three approaches are the use of volunteers, making a profit, and
getting funds from sponsors.
Networks like Tor rely on volunteers to provide the relays that make up the network.
Thousands of people around the world have computers with good network connections and want
to help make the world a better place. By joining them into one big network, Tor ensures that
the network is independent from the organization writing the software; so the network will be
around down the road even if The Tor Project as an entity ceases to exist. Psiphon takes the
second approach: collecting money for service. They reason that if they can create a profitable
company, then that company will be able to fund the network on an ongoing basis. The third
approach is to rely on sponsors to pay for the bandwidth costs. The Java Anon Proxy or JAP
project relied on government grants to fund its bandwidth; now that the grant has finished
they're investigating the for-profit approach. Ultrareach and Freegate use the sponsor model to
good effect, though they are constantly hunting for more sponsors to keep their network
After asking about the long-term survival of the network, the next question to ask is about
sustainability of the software itself. The same three approaches apply here, but the examples
change. While Tor's network is operated by volunteers, Tor relies on sponsors (governments and
NGOs) to fund new features and software maintenance. Ultrareach and Freegate, on the other
hand, are in a more sustainable position with respect to software updates: they have a team of
individuals around the world, mostly volunteers, devoted to making sure the tools are one step
ahead of censors.
Each of the three approaches can work, but understanding the approach a tool uses can help
you predict what problems it might encounter in the future.
4. Has an open design
The first step to transparency and reusability of the tool's software and design is to distribute
the software (not just the client-side software, but also the server-side software) under an open
source license. Open source licenses mean that you can examine the software to see how it
really operates, and you have the right to modify the program. Even if not every user takes
advantage of this opportunity (many people just want to use the tool as-is), providing the option
makes it much more likely that the tool will remain safe and useful. Otherwise, you are forced to
trust that a small number of developers have thought of and addressed every possible problem.
Just having an open source licence is not enough. Trustworthy circumvention tools need to
provide clear, complete documentation for other security experts not just about how it's built
but what features and goals its developers aimed for. Do they intend for it to provide privacy?
What kind and against what attackers? In what way does it use encryption? Do they intend for it
to stand up to attacks from censors? What kind of attacks do they expect to resist and why will
their tool resist them? Without seeing the source code and knowing what the developers meant
for it to do, it's harder to decide whether there are security problems in the tool, or to evaluate
whether it will reach its goals.
In the field of cryptography, Kerckhoffs' principle explains that you should design your system so
the amount you need to keep secret is as small and well-understood as possible. That's why
crypto algorithms have keys (the secret part) and the rest can be explained in public to anybody.
Historically, any crypto design that has a lot of secret parts has turned out to be less safe than
its designers thought. Similarly, in the case of secret designs for circumvention tools, the only
groups examining the tool are its original developers and its attackers; other developers and
users who could help to make it better and more sustainable are left out.
Ideas from one project could be reusable beyond that project's lifetime. Too many circumvention
tools keep their designs secret, hoping that government censors will have a harder time figuring
out how the system works, but the result is that few projects can learn from other projects and
the field of circumvention development as a whole moves forward too slowly.
5. Has a decentralized architecture
Another feature to look for in a circumvention tool is whether its network is centralized or
decentralized. A centralized tool puts all of its users' requests through one or a few servers that
the tool operator controls. A decentralized design like Tor or JAP sends the traffic through
multiple different locations, so there is no single location or entity that gets to watch what
websites each user is accessing.
Another way to look at this division is based on whether the trust is centralized or decentralized.
If you have to put all your trust in one entity, then the best you can hope for is "privacy by
policy" meaning they have all your data and they promise not to look at it, lose it, or sell it. The
alternative is what the Ontario Privacy Commissioner calls "privacy by design" meaning the
design of the system itself ensures that users get their privacy. The openness of the design in
turn lets everybody evaluate the level of privacy provided.
This concern isn't just theoretical. In early 2009 Hal Roberts from the Berkman Center ran
across a FAQ entry for a circumvention tool that offered to sell its users' clicklogs. I later talked
to a different circumvention tool provider who explained that they had all the logs of every
request ever made through their system "because you never know when you might want them."
I've left out the names of the tools here because the point is not that some tool providers may
have shared user data; the point is that any tool with a centralized trust architecture could
share user data, and its users have no way to tell whether it's happening. Worse, even if the tool
provider means well, the fact that all the data flows through one location creates an attractive
target for other attackers to come snooping.
Many of these tools see circumvention and user privacy as totally unrelated goals. This
separation isn't necessarily bad, as long as you know what you're getting into for example, we
hear from many people in censoring countries that just reading a news website isn't going to get
you locked up. But as we've been learning in many other contexts over the past few years, large
databases of personal information tend to end up more public than we'd like.
6. Keeps you safe from websites too
Privacy isn't only about whether the tool operator can log your requests. It's also about whether
the websites you visit can recognize or track you. Remember the case of Yahoo turning over
information about one of its Chinese webmail users? What if a blog aggregator wants to find out
who's posting to a blog, or who added the latest comment, or what other websites a particular
blogger reads? Using a safer tool to reach the website means the website won't have as much to
hand over.
Some circumvention tools are safer than others. At one extreme are open proxies. They often
pass along the address of the client with their web request, so it's easy for the website to learn
exactly where the request is coming from. At the other extreme are tools like Tor that include
client-side browser extensions to hide your browser version, language preference, browser
window size, time zone, and so on; segregate cookies, history, and cache; and prevent plugins
like Flash from leaking information about you.
This level of application-level protection comes at a cost though: some websites don't work
correctly. As more websites move to the latest "web 2.0" fads, they require more and more
invasive features with respect to browser behavior. The safest answer is to disable the
dangerous behaviors but if somebody in Turkey is trying to reach YouTube and Tor disables his
Flash plugin to keep him safe, his videos won't work.
No tools have solved this trade-off well yet. Psiphon manually evaluates each website, and
programs its central proxy to rewrite each page. Mostly they do this rewriting not for privacy
but to make sure all links on the page lead back to their proxy service, but the result is that if
they haven't manually vetted your destination site yet, it probably won't work for you. As an
example, they seem to be in a constant battle to keep up with Facebook's changing front page.
Tor currently disables some content that is probably safe in practice, because we haven't figured
out a good interface to let the user decide in an informed way. Still other tools just let through
any active content, meaning it's trivial to unmask their users.
7. Doesn't promise to magically encrypt the entire Internet
I should draw a distinction here between encryption and privacy. Most circumvention tools (all
but the really simple ones like open proxies) encrypt the traffic between the user and the
circumvention provider. They need this encryption to avoid the keyword filtering done by such
censors as China's firewall. But none of the tools can encrypt the traffic between the provider
and the destination websites if a destination website doesn't support encryption; there's no
magic way to make the traffic encrypted.
The ideal answer would be for everybody to use https (also known as SSL) when accessing
websites, and for all websites to support https connections. When used correctly, https provides
encryption between your web browser and the website. This "end-to-end" encryption means
nobody on the network (not your ISP, not the backbone Internet providers, and not your
circumvention provider) can listen in on the contents of your communication. But for a wide
variety of reasons, pervasive encryption hasn't taken off. If the destination website doesn't
support encryption, the best you can do is 1) not send identifying or sensitive information, such
as a real name in a blog post or a password you don't want other people to learn, and then 2)
use a circumvention tool that doesn't have any trust bottlenecks that allow somebody to link
you to your destinations despite the precautions in step 1.
Alas, things get messy when you can't avoid sending sensitive info. Some people have expressed
concern over Tor's volunteer-run network design, reasoning that at least with the centralized
designs you know who runs the infrastructure. But in practice it's going to be strangers reading
your traffic either way. The trade-off is between volunteer strangers who don't know it's you
(meaning they can't target you), or dedicated strangers who get to see your entire traffic profile
(and link you to it). Anybody who promises "100% security" is selling something.
8. Provides consistently good latency and throughput
The next feature you might look for in a circumvention tool is speed. Some tools tend to be
consistently fast, some consistently slow, and some provide wildly unpredictable performance.
Speed is based on many factors, including how many users the system has, what the users are
doing, how much capacity there is, and whether the load is spread evenly over the network.
The centralized-trust designs have two advantages here. First, they can see all their users and
what they're doing, meaning they have a head start at spreading them out evenly and at
discouraging behaviors that tax the system. Second, they can buy more capacity as needed, so
the more they pay the faster the tool is. The distributed-trust designs on the other hand have a
harder time tracking their users, and if they rely on volunteers to provide capacity, then getting
more volunteers is a more complex process than just paying for more bandwidth.
The flip side of the performance question is flexibility. Many systems ensure good speed by
limiting what their users can do. While Psiphon prevents you from reaching sites that they
haven't manually vetted, Ultrareach and Freegate actually actively censor which destination
websites you're allowed to reach so they can keep their bandwidth costs down. Tor, by contrast,
lets you access any protocol and destination, meaning for example you can instant message
through it too; but the downside is that the network is often overwhelmed by users doing bulk
9. Makes it easy to get the software and updates
Once a circumvention tool becomes well-known, its website is going to get blocked. If it's
impossible to get a copy of the tool itself, who cares how good it is? The best answer here is to
not require any specialized client software. Psiphon, for example, relies on a normal web
browser, so it doesn't matter if the censors block their website. Another approach is a tiny
program like Ultrareach or Freegate that you can instant message to your friends. Option three
is Tor's Browser Bundle: it comes with all the software you need preconfigured, but since it
includes large programs like Firefox it's harder to pass around online. In that case distribution
tends to be done through social networks and USB sticks, or using our e-mail autoresponder that
lets you download Tor via Gmail.
Then you need to consider the trade-offs that come with each approach. First, which operating
systems are supported? Psiphon does well here too by not requiring any extra client software.
Ultrareach and Freegate are so specialized that they only work on Windows, whereas Tor and its
accompanying software can run pretty much everywhere. Next, consider that client-side
software can automatically handle failover from one proxy to the next, so you don't need to
manually type in a new address if your current address disappears or gets blocked.
Last, does the tool have a track record for responding to blocking? For example, UltraSurf and
Freegate have a history of releasing quick updates when the current version of their tool stops
working. They have a lot of experience at this particular cat-and-mouse game, so it's reasonable
to assume they're ready for the next round. Along these lines, Tor prepared for its eventual
blocking by streamlining its network communications to look more like encrypted web browsing,
and introducing unpublished "bridge relays" that are harder for an attacker to find and block than
Tor's public relays. Tor tries to separate software updates from proxy address updates. If the
bridge relay you're using gets blocked, you can stick with the same software and just configure it
to use a new bridge address. Our bridge design was put to the test in China in September of
2009, and tens of thousands of users seamlessly moved from the public relays to bridges.
10. Doesn't promote itself as a circumvention tool
Many circumvention tools launch with a huge media splash. The media loves this approach, and
they end up with front page articles like "American hackers declare war on China!" But while this
attention helps attract support (volunteers, profit, sponsors), the publicity also attracts the
attention of the censors.
Censors generally block two categories of tools: 1) the ones that are working really well, meaning
they have hundreds of thousands of users, and 2) the ones that make a lot of noise. In many
cases censorship is less about blocking all sensitive content and more about creating an
atmosphere of repression so people end up self-censoring. Articles in the press threaten the
censors' appearance of control, so they are forced to respond.
The lesson here is that we can control the pace of the arms race. Counterintuitively, even if a
tool has many users, as long as nobody talks about it much it tends not to get blocked. But if
nobody talks about it, how do users learn about it? One way out of the paradox is to spread
through word of mouth and social networks rather than the more traditional media. Another
approach is to position the tool in a different context; for example, we present Tor primarily as a
privacy and civil liberties tool rather than a circumvention tool. Alas, this balancing act is tough
to maintain in the face of increasing popularity.
This article explains some of the issues you should consider when evaluating the strengths and
weaknesses of circumvention tools. I've intentionally avoided drawing up a table of different tools
and scoring them on each category. No doubt somebody will do that eventually and sum up how
many checkmarks each tool gets, but the point here is not to find the "best" tool. Having a
diversity of circumvention tools in wide use increases robustness for all the tools, since censors
have to tackle every strategy at once.
Last, we should keep in mind that technology won't solve the whole problem. After all, firewalls
are socially very successful in these countries. As long as many people in censored countries are
saying "I'm so glad my government keeps me safe on the Internet," the social challenges are at
least as important. But at the same time, there are people in all of these countries who want to
learn and spread information online, and a strong technical solution remains a critical piece of the
Roger Dingledine is project leader for The Tor Project, a US non-profit working on anonymity
research and development for such diverse organizations as the US Navy, the Electronic Frontier
Foundation, and Voice of America. In addition to all the hats he wears for Tor, Roger organizes
academic conferences on anonymity, speaks at a wide variety of industry and hacker
conferences, and also does tutorials on anonymity for national and foreign law enforcement.
This article is licensed under the Creative Commons Attribution 3.0 United States License.
Originally prepared for the March 2010 "Index on Censorship", then adapted for the July 2010
"China Rights Forum" (Chinese translation). Last updated 25 May 2010.
Bypassing Internet censorship is a big topic, with dozens of tools and services available. There
are also lots of things to consider if you want your circumvention activities to be harder to
detect or to block in the future, if you want to achieve anonymity in your Internet use, or if you
want to help other people circumvent censorship. Here are some recommended resources for
further study about related matters. (Some of these resources may be unavailable or blocked in
some places.)
Circumventing Internet censorship
Reporters Without Borders, Handbook for Bloggers and Cyber-Dissidents,
The Internet Censorship Wiki,
Computer security advice for activists
NGO-in-a-Box, a collection of free portable applications,
Digital Security and Privacy for Human Rights Defenders,
Surveillance Self-Defense International,
Studies on Internet censorship
Ronald Deibert, John Palfrey, Rafal Rohozinski, Jonathan Zittrain, Access Denied: The Practice
and Policy of Global Internet Filtering (Cambridge, MA: MIT Press, 2008), ISBN 0-262-541963
Ronald Deibert, John Palfrey, Rafal Rohozinski, Jonathan Zittrain, Access Controlled: The
Shaping of Power, Rights, and Rule in Cyberspace (Cambridge, MA: MIT Press, 2010), ISBN 0262-51435-4
Hal Roberts, Ethan Zuckerman, Jillian York, Rob Faris, John Palfrey, 2010 Circumvention Tool
Usage Report (Berkman Center for Internet & Society)
More resources on Internet censorship:
Citizen Lab (
Committee to Protect Bloggers (
Committee to Project Journalists (
Berkman Center for Internet and Society (
Electronic Frontier Foundation (
FrontLine (
Global Internet Freedom Consortium (
The Herdict (
OpenNet Initiative (
Peacefire (
Reporters Sans Frontières/Reporters Without Borders (
Sesawe (
Tactical Tech Collective (
221, a list of thousands of open Web Proxies:
Peacefire, a mailing list which sends out new web proxies:,
Application proxies:
Access Flickr!:
Circumventor CGIProxy:
Dynaweb FreeGate:
Hamachi LogMeIn:
HTTPS Everywhere:
JAP / JonDo:
UltraReach UltraSurf:
A list of commercial VPN providers
Socksification software (to make non-proxy aware software work with a
SOCKS proxy)
All chapters copyright of the authors (see below). Unless otherwise stated all chapters in this
manual licensed with GNU General Public License version 2.
This documentation is free documentation; you can redistribute it and/or modify it under the
terms of the GNU General Public License as published by the Free Software Foundation; either
version 2 of the License, or (at your option) any later version.
This documentation is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with this
documentation; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
Boston, MA 02110-1301, USA.
All chapters © the contributors unless otherwise noted below.
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Free manuals for free software
Version 2, June 1991
Copyright (C) 1989, 1991 Free Software Foundation, Inc.
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
The licenses for most software are designed to take away your freedom to share and change it.
By contrast, the GNU General Public License is intended to guarantee your freedom to share and
change free software--to make sure the software is free for all its users. This General Public
License applies to most of the Free Software Foundation's software and to any other program
whose authors commit to using it. (Some other Free Software Foundation software is covered by
the GNU Lesser General Public License instead.) You can apply it to your programs, too.
When we speak of free software, we are referring to freedom, not price. Our General Public
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you want it, that you can change the software or use pieces of it in new free programs; and that
you know you can do these things.
To protect your rights, we need to make restrictions that forbid anyone to deny you these rights
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you if you distribute copies of the software, or if you modify it.
For example, if you distribute copies of such a program, whether gratis or for a fee, you must
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can get the source code. And you must show them these terms so they know their rights.
We protect your rights with two steps: (1) copyright the software, and (2) offer you this license
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making the program proprietary. To prevent this, we have made it clear that any patent must
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The precise terms and conditions for copying, distribution and modification follow.
0. This License applies to any program or other work which contains a notice placed by the
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in any medium, provided that you conspicuously and appropriately publish on each copy an
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distribute them as separate works. But when you distribute the same sections as part of a
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or collective works based on the Program.
In addition, mere aggregation of another work not based on the Program with the Program (or
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bring the other work under the scope of this License.
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code or executable form under the terms of Sections 1 and 2 above provided that you also do
one of the following:
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interchange; or,
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Program subject to these terms and conditions. You may not impose any further restrictions on
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reason (not limited to patent issues), conditions are imposed on you (whether by court order,
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from the conditions of this License. If you cannot distribute so as to satisfy simultaneously your
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and a licensee cannot impose that choice.
This section is intended to make thoroughly clear what is believed to be a consequence of the
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patents or by copyrighted interfaces, the original copyright holder who places the Program under
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