Five components of WLAN Security
1. Data Privacy
1. Privacy is important because transmission occurs over the air in freely
licensed bands. The Data can be sniffed by anyone within range.
2. Eavesdropping – Also referred to war driving. Many free utilities exist to
find WLAN's (Such NetStumbler and InSSIDer) These programs broadcast
null probe request across all channels forcing the AP's to respond. (With
the SSID, Channel, Encryption Type, etc). Casual eavesdropping is
considered harmless. However this can be performed with a protocol
analyzer and legitimate data can be captured. This is also known as a
passive attack
2. AAA
1. Authentication - Verification of credentials
2. Authorization - Granting access to resources.
3. Accounting - Audit of what was accessed by who.(This is important for
HIPAA compliance)
3. Segmentation
1. Access/Role segmentation via RBAC.
1. RBAC provides restricted access to authorized users. May restrict
bandwidth usage and port access.
2. Network segmentation via Firewalls or VLANs.
1. VLANs provide different networks for different SSID's depicting
different security or QoS rules.
4. Monitoring
1. Provided by a WIPS or WIDS, that watches for Layer 1/2 attacks.
2. Spectrum Analysis can be performed to find sources of interference at
layer 1.
5. Security Policy
Legacy Security
Open System - No/Null authentication, anyone is able to join. Performed as a two way
handshake.
WEP - Wired Equivalent Privacy, a Shared key authentication to prevent casual
eavesdropping. The key is configured on the both the access point and the client. This
WEP key is used to encrypt all 802.11 data frames. Can keys can either be ASCII or Hex
characters. RADIUS can use dynamic WEP keys on a per-packets basis, enhancing
security WEP however is still weak.
Image: WEP Authentication process
Integrity Check Value ICV is ran against the data prior to encryption and is used to
prevent the data from being altered.
64-Bit WEP uses a 40-Bit static key and a 24-bit Initialization Vector (IV) The IV is
sent in clear text and changes every frame. However their are only 16,777,216 different
combinations.
Key Length 10 Hex or 5 ASCII
128-Bit WEP used a 104-Bit static key and 24-Bit IV.
Key Length 26 Hex or 13 ASCII
WEP Weaknesses:
IV Collision Attacks - Since their are only 16 Million different IVs they will repeat and the
attacker will be able to recover the key.
Weak key Attack - Weak keys are created due to the RC4's key scheduling algorithm.
Reinjection Attack - An attacker using a packet injector (such as AirPCap Nx or Scapy) to
inject packets forcing the use of addition IV's. This allows the IV's to be used sooner.
Bit Flipping Attack - Data Integrity is weak and the data can be altered.
Note: Current Free tools can crack WEP in as little as 5 minutes such airodump or aircrack.
MAC Filtering - Only allows specific MAC address access to the WLAN. MAC Address can be
easily spoofed by various open source and free tools, and sometimes this can be changed within
the device properties.
SSID Cloaking - Also called closed network. The SSID field in a beacon frame is simply
empty/Null. This can be easily found by Layer 2 analyzers and sniffers such as
NetStumbler/AirPCap/Omnipeek. This can also cause addition overhead to IT staff since the
SSID needs to be configured on WLAN client. This feature may also cause issues with legacy
WLAN cards.
Image: Beacon Frame with no SSID information
Modern Security
4 Way handshake - The creation of dynamic encryption keys 5 separate keys are
created in this process two master keys Group master keys (GMK) and the Pairwise
Master Key (PMK). The keys are seeding to form the dynamic keys for encrypting the
data. The final two keys are the pairwise transient key (PTK) and group temportal key
(GTK) which are used to encrypt/decrypt unicast traffic.
RSN Robust Security Network - States 2 STA's must generate dynamic encryption keys
through a 4-way handshake this is referred to as an RSNA Robust Security Network
Association. This generated encryption key is specific to the 2 WLAN radios.
RSN is also identified by a the Information Element IE field found within the beacon
frame.
Image: RSN Information within a beacon frame
Image: You can see the client initiating the EAPOL (EAP Over LAN) transaction with the Cisco
AP.
Passphrase based security
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Creates a 256 bit PSK to communicate with WLAN
8-53 ASCII characters can be used for the key or 64 Hex
Longer the passphrase the more secure it is
weak pass phrases can be easily compromised.
TKIP Temporal Key Integrity Protocol - Designed as a software upgrade from WEP. This was
the foundation for the WPA certification from the Wi-Fi Alliance. EoL with 802.11i, however
802.11i is backward compatible with WPA
Enhancements in TKIP:
1. Use of RC4 stream cipher for backward compatibility with WEP.
2. RC4 is used with WEP Encryption, RC4 is not a weak algorithm it was just implemented
poorly.
3. RC4 uses key strengths of 64 or 128 Bits. RC4 is also used in SSL connections.
4. Dynamic re-keying mechanism to change encryption and integrity keys. IV is mixed with
the secret root key then sent to RC4
5. Per packet key mixing of the IV to separate weak keys.
6. Uses a 48 bit IV compared to the 24 bit used by WEP
7. 64 Bit MIC Message Integrity Check
8. Message Integrity Check/MIC Prevents data from being tampered with
1. If MIC's do not match the data is assumed to have been altered and all clients will
be DeAuthenticated and stopping new associations for 1 minute.
9. Sequence Counters to protect from replay attacks
The 802.11i standard, now part of the 802.11-2007 standard, requires 802.1X/EAP in
the enterprise and PSK (Pre-Shared Keys) for SOHO deployments. CCMP/AES is the
required encryption method. TKIP/RC4 is optional. EAP is also a layer 2 protocol.
CCMP Counter mode with Cipher block Chaining Message authentication code Protocol Mandatory in the 802.11i amendment, also part of WPA2, uses the AES algorithm. Wi-Fi
uses 128 bit blocks.
1. AES has been cracked but requires extreme measures. Side Channel attacks.
2. AES/CCMP - requires more processor power and typically requires a hardware upgrade
compared to a typical software upgrade for TKIP
3. AES Meets FIPS140-2 Complaint
802.11 Frames and Encryption
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Management frames are not encrypted.
Control frames do not have a body and are not encrypted.
Data frames - The MSDU inside the body is encrypted. This is a layer 2 encryption that
protects information through layer 3 - 7.
Image: You can see the TKIP Parameters, and the data is in cipher text.
802.1X Authentication (framework) - Initially used for wired port based authentication,
also now used with WLANs.
Involves
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Supplicant - Client device trying to connect
Authenticator - middle man devices (AP/Switch/WLC) that passes on
authentication information to authentication serve. This device does not allow
network access until the the authentication is successful.
Authentication Server - Receives information from authenticator and verifies
credentials using a user DB (internal or external)
Image: 802.1X authentication process.
EAP Extensible Authentication Protocol - Authentication process used with 802.1X
Common EAP types:
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EAP-TLS - Requires PKI on client and server. Most secure.
EAP-TTLS - TLS Tunnel, Requires server side certificate.
PEAP - Protected EAP. Microsoft Supported by MS-CHAP Only server side certificate.
EAP-FAST - From Cisco uses PAC Protected Access Control no PKI required. Uses MSCHAPv2
LEAP - Uses with MS-CHAPv2 supported with MS passwords and certificates.
More information can be found
here: http://en.wikipedia.org/wiki/Extensible_Authentication_Protocol
Wi-Fi Protected Setup WPS - Another standard created by the Wi-Fi Alliance for simple secure
SOHO WLAN deployments. This may not be supported on older harder since this standard has
only been around since 2007.
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Pin Method - A pin number stamped on the AP needs to be entered on the client when
trying to associated to the access point.
PBC - Push Button Connection involves pressing a physical button when connecting the
access point
RBAC - Provides restricted access to authorized users. May restrict bandwidth usage and port
access, or even administrative access to IT personnel.
Secure Device Management - It is important to remember to manage and configure
devices using a secure protocols, this ensures the actual network devices cannot be
tampered with.
http://itnetworkingpros.wordpress.com/2011/03/10/secure-cisco-device-management/
Virtual Private Network /VPN - Private communication from a device over the internet to
a home/central office. Operate at Layer 3 (the network layer), still used for secure
connectivity through public hotspots.
Before 802.11i when Layer2 WLAN security was weak VPN was the primary way of securing
data over the WLAN. VPN's consist of 2 part Tunneling and Encryption (DES, 3DES, AES,
RC4, MD5, SHA1), a VPN will encapsulate one IP frame within another IP frame
2 Two common VPN protocols PPTP & IPSec - Provide user authentication, data encryption,
and integrity.
1. PPTP Point-to-Point Tunneling Protocol - Created by Microsoft, Built into windows and
was easy to configuration, encryption was provided by MPPE/RC4 Microsoft Point-toPoint Encryption. Utilizes MS-CHAPv2, which is susceptible to dictionary attacks.
2. L2TP Layer 2 Tunneling Protocol - Based off Cisco L2F (Layer 2 Forwarding) and
Microsoft's PPTP.Requires IPSec (utilizing IKE) for encryption and is more secure then
PPTP
3. WebVPN - SSL/TLS Connections via web browsers.
Network Security Analysis, Performance Analysis, and troubleshooting
Common threats to WLAN's
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Eavesdropping
RF DoS
MAC Spoofing
Hijacking
Man in the middle attacks
P2P attacks
Encryption cracking
Wi-Fi Alliance certification:
WPA-Personal
Passphrase
TKIP/RC4
WPA-Enterprise
802.1X/EAP TKIP/RC4
WPA2-Personal
Passhprase
CCMP/AES or TKIP/RC4
WPA2-Enterprise
802.1X/EAP CCMP/AES or TKIP/RC4
Wireless Intrusion Detection Systems WIDS - Works at layers 1 and 2 to watch
for possible attacks (such as DoS and Wi-Fi Hijacking). A typical WIDS deployment
involves a server, management console, and sensors. The sensors do not provide WLAN
access to clients but instead just watch the RF medium.
Image: Common attacks a WIPS can protect from.
Deployment Methods:
1. Overlay - Deployed over existing WLAN
2. Integrated - Part of the WLC/LWAP Model. The LWAPs are able to act like sensors.
3. Integration Enabled - The Existing hardware is capable of being integrated with the
management interface of WIDS server software.
Wireless Intrusion Prevention Systems WIPS - Similar to a WIDS except the WIPS is capable
of mitigating attacks. WIPS classifies APs in one of four ways:
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Infrastructure - A legitimate network device.
Unknown - A detected device that has not yet been classified.
Known - A detected device that has been classified.
Rouge - A device that is not authorized or is seen to interfere with the WLAN
Many WIPS mitigate attacks differently, most commonly the AP will spoof the MAC address of
the rouge AP and send out DeAuth frames. Some vendors offer a mobile WIPS, which is simply
a laptop program that can find rouge devices and perform protocol analysis.
Image: DeAuth frame sent spoofed from a Cisco AP to an Ad Hoc connection.
Rouge Access Points - These devices can be setup by anyone (typically by an end
user). What makes these devices dangerous is the fact they can provide unauthorized
access to the wired network (and network resources).
Ad Hoc Networks - Known as an IBSS Independent Basic Service Set. Ad Hoc
networks allow computers to connect directly to each other without the use of an
access point allowing users to transfer and share files on the fly. Most WLANs have the
ability to block peer to peer connects using a technology called Public Secure Packet
Forwarding (PSPF)
Image: An Ad Hoc network from Windows Zero Config
Wireless Hijacking - Malicious users can install access point software to imitate an
access point that will allow unsuspecting users to connect to the malicious user allow all
the client to be capture and possibly tampered with.
DoS Attacks - Intentional attacks can be performed with Wi-Fi jamming devices.
Nothing can be done against these kind of attacks. These can also be unintentional (by
BlueTooth devices, cordless phones, microwaves
Spectrum Analysis:
Protocol Analysis:
Network Security Policies
Recommendations:
Remote Access Policy - For users that travel to remote off-site locations with laptops.
Typically mandate the use of a IPSec VPN, AV, and Firewall.
Rouge AP Policy - States End-users should not use their own type of WLAN AP/Router devices
Ad Hoc Policy - Prevent users from initiating peer to peer wireless connections
WLAN Proper Use Policy - Outline how the WLAN should used by the end users
IDS Policy - States how to respond to WIDS/WIPS events.
General Security Policy - Define how to deal with rouge devices.
Statement of authority - Defines the policy and that it is backed by management
Application audience - Defines who must abide by the policy.
Violation reporting procedures - Defines how the policy will be enforced.
Risk Assessment and threat analysis - What may happen if a successful compromise occurs.
Security Auditing - Define auditing procedures.
Functional Security Policy - Defines the technical aspects of WLAN security. Defines the
following:
Policy Essentials - Password policies, training, and proper WLAN usage.
Baseline practices - Configuration checklists.
Design and implementation - Defines the Encryption, encryption, segmentation policies.
Monitor and response - Defines IDS procedures and appropriate responses.
Captive Portal - SSL Web page that can require users to sign in and acknowledge a UAP.
Once authenticated to captive Internet traffic flows. Found at Hot spots, hotels, airports, etc.
Legislative Compliances
HIPPA - Found in the health care field to protect the medical records of patients.
1. HIPAA Title I - Protects health insurance of someone who loses/changes job
2. HIPAA Title II - Establishes mandatory regulations for health care providers for
securing computer data/information.
Sarbanes-Oxley - For financial institutes, dictates accounting and auditing.
Graham-Leach-Bhiley - Also for financial institutes to protect credit card, social security
numbers, names, addresses and so forth. (Personal information)
PCI Compliance - Payment Card Industry for protecting credit card information
6 Requirements:
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6.
Build and maintain and secure network/Firewall.
Protect card holder data/Encryption
Maintain a vulnerability management program
Implement strong access control measures
Regularly monitors and test networks
Maintain an information security policy