PVS 4.2 User Guide - Tenable Network Security

PVS 4.2 User Guide - Tenable Network Security
Passive Vulnerability Scanner 4.2
User Guide
March 26, 2015
(Revision 3)
Table of Contents
Introduction ............................................................................................................................................................... 5
Standards and Conventions....................................................................................................................................................................... 5
Passive Vulnerability Scanner Background and Theory .................................................................................................................. 5
Pre-Installation ......................................................................................................................................................... 6
Hardware requirements ............................................................................................................................................................................. 6
Software and Licensing ............................................................................................................................................................................... 6
Download or Obtain the Software........................................................................................................................................................... 6
PVS Subscription ......................................................................................................................................................................................... 7
SecurityCenter Continuous View ............................................................................................................................................................. 7
Activation Code ........................................................................................................................................................................................... 7
Upgrading ................................................................................................................................................................... 7
Upgrading PVS on Linux ............................................................................................................................................................................. 7
Upgrading PVS on Windows ..................................................................................................................................................................... 8
Upgrading PVS on Mac OS X .................................................................................................................................................................. 10
Initial Installation .................................................................................................................................................. 16
Linux Installation ........................................................................................................................................................................................ 16
Windows Installation ................................................................................................................................................................................ 16
Mac OS X Installation................................................................................................................................................................................ 25
Starting and Stopping PVS for Mac OS X ............................................................................................................................................ 31
Removing PVS ......................................................................................................................................................... 31
Removing PVS for Linux........................................................................................................................................................................... 31
Removing PVS for Windows................................................................................................................................................................... 32
Removing PVS for Mac OS X .................................................................................................................................................................. 32
Initial Configuration of the PVS Server .......................................................................................................... 32
Using the PVS Interface ....................................................................................................................................... 34
Navigation..................................................................................................................................................................................................... 35
Monitoring .................................................................................................................................................................................................... 37
Hosts Tab.................................................................................................................................................................................................... 40
Vulnerabilities Tab ................................................................................................................................................................................... 40
Applications Tab ....................................................................................................................................................................................... 41
Operating System Tab ............................................................................................................................................................................. 41
Connection Tab ......................................................................................................................................................................................... 41
Dashboard Tab ......................................................................................................................................................................................... 41
Dashboard Vulnerabilities Tab .............................................................................................................................................................................42
Dashboard Events Tab .............................................................................................................................................................................................42
Results ............................................................................................................................................................................................................ 44
Users ............................................................................................................................................................................................................... 44
Creating Users ........................................................................................................................................................................................... 44
Resetting User Passwords....................................................................................................................................................................... 45
Resetting Locked Accounts..................................................................................................................................................................... 45
Configuration............................................................................................................................................................................................... 46
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PVS Settings Tab ....................................................................................................................................................................................... 46
Feed Settings Tab ..................................................................................................................................................................................... 50
Web Proxy Settings Tab .......................................................................................................................................................................... 50
Chart Settings Tab.................................................................................................................................................................................... 51
Creating a Custom Chart ........................................................................................................................................................................ 51
Plugin Settings Tab................................................................................................................................................................................... 54
Enable/Disable Plugins Action Screen ...............................................................................................................................................................54
Enable/Disable PASLs Action Screen .................................................................................................................................................................55
Create Plugin Action Screen ..................................................................................................................................................................................56
Command Line Operation ................................................................................................................................... 58
Command Line Operations for Linux .................................................................................................................................................. 59
Starting the Passive Vulnerability Scanner for Linux ....................................................................................................................... 59
Stopping the Passive Vulnerability Scanner for Linux...................................................................................................................... 59
File Locations ............................................................................................................................................................................................. 59
Command Line Operations for Windows .......................................................................................................................................... 60
File Locations ............................................................................................................................................................................................. 61
Starting and Stopping PVS ..................................................................................................................................................................... 62
Command Line Operations for Mac OS X.......................................................................................................................................... 62
Stopping the Passive Vulnerability Scanner for Mac OS X.............................................................................................................. 62
File Locations ............................................................................................................................................................................................. 62
Common Command Line Options ........................................................................................................................................................ 63
Define Unknown or Customized Ports................................................................................................................................................. 65
PVS Realtime Traffic Analysis Configuration Theory ............................................................................... 65
Focus Network ............................................................................................................................................................................................ 65
Detecting Server and Client Ports ....................................................................................................................................................... 66
Detecting Specific Server and Client Port Usage............................................................................................................................ 66
What this Means for Firewall Rules ..................................................................................................................................................... 67
Working with the SecurityCenter ........................................................................................................................................................ 67
Selecting Rule Libraries and Filtering Rules...................................................................................................................................... 67
Detecting Encrypted and Interactive Sessions ................................................................................................................................ 68
Routes and Hop Distance ........................................................................................................................................................................ 68
Alerting .......................................................................................................................................................................................................... 69
New Host Alerting ..................................................................................................................................................................................... 69
Internal Passive Vulnerability Scanner IDs .................................................................................................. 69
What is a Passive Vulnerability Scanner ID? .................................................................................................................................... 69
Internal Passive Vulnerability Scanner IDs ....................................................................................................................................... 69
Working with Passive Vulnerability Scanner Plugins .............................................................................. 70
Vulnerability and Passive Fingerprint Overview ............................................................................................................................ 70
Downloading New Vulnerability Plugins ............................................................................................................................................ 71
Writing Custom Plugin Libraries ........................................................................................................................................................... 71
Restarting the Passive Vulnerability Scanner .................................................................................................................................... 71
Writing Passive Vulnerability Scanner Plugins................................................................................................................................ 71
Plugin Keywords ....................................................................................................................................................................................... 71
Plugin Libraries ......................................................................................................................................................................................... 73
Basic Passive Vulnerability Scanner Example.................................................................................................................................... 74
More Complex Passive Vulnerability Scanner Example .................................................................................................................. 74
Case Insensitive Example........................................................................................................................................................................ 75
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Passive Vulnerability Scanner Network Client Detection ............................................................................................................... 75
The Passive Vulnerability Scanner can Match “Previous” Packets ............................................................................................... 76
The Passive Vulnerability Scanner can Match Binary Data ........................................................................................................... 76
Negative Matches..................................................................................................................................................................................... 77
Time Dependent Plugins ......................................................................................................................................................................... 78
Writing Passive Vulnerability Scanner Realtime Plugins ............................................................................................................. 79
Realtime Plugin Model ............................................................................................................................................................................ 79
Keywords .................................................................................................................................................................................................... 79
Example Failed Telnet Login Plugin...................................................................................................................................................... 79
Example Finger User List Enumeration Plugin ................................................................................................................................... 80
Example Unix Password File Download Web Server Plugin ........................................................................................................... 80
Example Generic Buffer Overflow Detection on Windows Plugin ................................................................................................ 81
Passive Vulnerability Scanner Corporate Policy Plugins ............................................................................................................. 82
Detecting Custom Activity Prohibited by Policy ............................................................................................................................... 83
Detecting Confidential Data in Motion ............................................................................................................................................... 84
Passive Vulnerability Scanner Operating System Fingerprints ............................................................ 86
Passive Operating System Fingerprinting ......................................................................................................................................... 86
For Further Information....................................................................................................................................... 86
About Tenable Network Security ...................................................................................................................... 86
Appendix 1: Working with SecurityCenter .................................................................................................... 87
Architecture ................................................................................................................................................................................................. 87
Managing Vulnerabilities......................................................................................................................................................................... 87
Updating the PVS Management Interface......................................................................................................................................... 87
The Passive Vulnerability Scanner is Realtime ................................................................................................................................ 87
Appendix 2: Syslog Message Formats............................................................................................................. 88
Appendix 3: PVS Activation without Internet Access ............................................................................... 90
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Introduction
This document describes the Passive Vulnerability Scanner 4.2 (Patent 7,761,918 B2) architecture, installation, operation,
integration with SecurityCenter, and export of data to third parties. Please email any comments and suggestions to
[email protected]
The Passive Vulnerability Scanner 4.2 is available for the following platforms:




Red Hat Linux ES 5 / CentOS 5 64-bit
Red Hat Linux ES 6 / CentOS 6 64-bit
Mac OS X 10.8 and 10.9 64-bit
Microsoft Windows Vista, 7, 8, Server 2008, and Server 2012
This document describes the Passive Vulnerability Scanner installation and operation on the Red Hat Linux, Mac OS X, and
Microsoft Windows platforms and includes the theory and operational details related to the implementation.
Standards and Conventions
Throughout the documentation, filenames, daemons, and executables are indicated with a courier bold font such as
gunzip, httpd, and /etc/passwd.
Command line options and keywords are also indicated with the courier bold font. Command line examples may or may
not include the command line prompt and output text from the results of the command. Command line examples will display
the command being run in courier bold to indicate what the user typed while the sample output generated by the system
will be indicated in courier (not bold). Following is an example running of the Unix pwd command:
# pwd
/opt/pvs
#
Important notes and considerations are highlighted with this symbol and grey text boxes.
Tips, examples, and best practices are highlighted with this symbol and white on blue text.
Passive Vulnerability Scanner Background and Theory
Passive vulnerability scanning is the process of monitoring network traffic at the packet layer to determine topology, clients,
applications, and related security issues. Tenable has expanded the functionality of the Passive Vulnerable Scanner (PVS) to
include traffic profiling and system compromise detection. PVS can:

detect when systems are compromised based on application intrusion detection

highlight all interactive and encrypted network sessions

detect when new hosts are added to a network

track exactly which systems communicate with other systems and on what ports

detect what ports are served and what ports are browsed by each system

detect how many hops away each monitored host is
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This document provides directions for deploying, configuring, and operating the PVS.
Pre-Installation
To ensure a streamlined installation process, it is important to ensure that the appropriate hardware, software, and licensing
requirements are in place prior to installation.
Hardware requirements
Enterprise networks can vary in performance, capacity, protocols, and overall activity. Resource requirements to consider
for PVS deployments include raw network speed, the size of the network being monitored, and the configuration of the PVS
application.
The following chart outlines some basic hardware requirements for operating PVS:
Scenario
Minimum Recommended Hardware
Passive Vulnerability Scanner managing up to
50,000 hosts * (**)
CPU: 1 dual-core 2 GHz CPU
Memory: 2 GB RAM (4 GB RAM recommended)
Passive Vulnerability Scanner managing in
excess of 50,000 hosts **
CPU: 1 dual-core 3 GHz CPU (2 dual-core recommended)
Memory: 4 GB RAM (8 GB RAM recommended)
* Note: The ability to monitor a given number of hosts rests heavily on the bandwidth, memory, and processor
power available to the system running PVS.
Please research your VM software vendor for comparative recommendations as VMs typically see up to a 30%
loss in efficiency compared with dedicated servers.
** Note: For optimal data collection, PVS needs to be connected to the network segment via a hub, spanned port,
or network tap to have full continuous view of the data stream.
Processor requirements will increase with greater throughput and number of network interfaces. Memory requirements will
increase for networks with more hosts. The requirements for both of these components are affected by options such as a
long report-lifetime and enabling some or all of the PVS optional services in the configuration file.
Disk space requirements for PVS will vary depending on usage based on the amount and length of time data is stored on the
system.
Software and Licensing
Download or Obtain the Software
To install the PVS, obtain the correct version for your desired operating system from the “Downloads” section of the Tenable
Support Portal. Confirm the integrity of the installation package by comparing the download MD5 checksum with the one
listed in the product release notes.
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It is important to ensure that the correct build for your operating environment is downloaded to ensure binary
compatibility.
PVS Subscription
A PVS subscription Activation Code is available to enable PVS to operate in a stand-alone mode. This mode enables the PVS
results to be viewed from a HTML interface enabled on the PVS server.
SecurityCenter Continuous View
Continuous View includes PVS as part of a bundled license package with SecurityCenter. This license allows an unlimited
number of PVS deployments to monitor an unlimited number of networks. SecurityCenter’s IP view will be constrained by
the license purchased with it.
Activation Code
To obtain an evaluation Activation Code for PVS, contact [email protected] Evaluation Activation Codes are handled the
same way by the PVS as a full Activation Code, except that an evaluation Activation Code will only allow monitoring for 30
days. During an evaluation of the PVS, all of the features are available.
Upgrading
This section describes the steps to upgrade an existing PVS installation on Linux and Windows platforms. During the upgrade
process on both platforms, items that are commented out in the configuration file are not migrated. Review the configuration
file for any information that may need to be preserved.
Upgrading PVS on Linux
Before upgrading, the PVS services must be stopped. Failure to do so may result in errors. Custom SSL certificates
must be backed up before an upgrade. It is assumed that all commands are run with root privileges.
If you have used a PVS RPM to install PVS previously, an upgrade retains configuration settings.
Transfer the PVS RPM package to the system it is being installed on. Confirm the integrity of the installation package by
comparing the download md5 checksum with the one listed in the product release notes.
Before upgrading you will first need to stop the PVS service:
# service pvs stop
Copy the file /opt/pvs/var/pvs/tenable.key to the machine that will be used to configure the PVS after the upgrade
is complete.
Install the PVS software with the following command. Note that the specific filename will vary, depending on your version:
# rpm -Uvh pvs-4.x.x-es6.x86_64.rpm
Preparing...
########################################### [100%]
1:pvs
########################################### [100%]
[*] PVS installation completed.
#
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Once the upgrade is complete, start the PVS service with the following command:
# service pvs start
After starting PVS, navigate to https://<ipaddress or hostname>:8835, which will display the PVS web frontend to
log in for the first time. Follow the directions described in the section Initial Configuration of the PVS Server to complete the
initial login.
Ensure that organizational firewall rules permit access to port 8835 on the PVS server.
Upgrading PVS on Windows
Before upgrading, the PVS services must be stopped. Failure to do so may result in errors. Custom SSL
certificates must be backed up before an upgrade. All programs are run as a local administrator user. When UAC
is enabled, right click on the installer program and select “Run as Administrator”.
Ensure that the latest version of the Microsoft Visual C++ 2010 Redistributable Package for your 64-bit
platform and architecture is installed prior to PVS software installation.
Prior to upgrading PVS, ensure that any other programs on the system utilizing WinPcap are stopped.
Stop the Tenable PVS Proxy Service from the Windows Services control panel.
Copy the file C:\ProgramData\Tenable\PVS\pvs\tenable.key to the machine that will be used to configure the PVS
after the upgrade is complete.
Start the PVS software for Windows upgrade by double-clicking on the .exe file downloaded from Tenable. Note that the
specific filename will vary, depending on your platform and/or version:
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This will start the upgrade process by launching the InstallShield Wizard:
Clicking the “Next” button will begin the automated upgrade process. If the version of WinPcap is not at the appropriate
level during the upgrade process, an upgrade window will be displayed to begin the process of upgrading WinPcap. Failure to
install the recommended version of WinPcap may result in error with PVS monitoring.
Once completed, the Installation process will exit.
After starting the PVS, navigate to https://<ipaddress or hostname>:8835 to display the PVS web frontend to log
in for the first time. Follow the directions described in the section Initial Configuration of the PVS Server to complete the
initial login.
Ensure that organizational firewall rules permit access to port 8835 on the PVS server.
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Upgrading PVS on Mac OS X
Before upgrading, the PVS services must be stopped. Failure to do so may result in errors. See the “Starting and
Stopping PVS for Mac OS X” section for instructions. Custom SSL certificates must be backed up before an
upgrade. All programs are run as a root user.
Begin upgrading the PVS software for Mac OS X by double clicking on the .dmg file downloaded from the Tenable Support
Portal to mount the disk image “PVS Install”. Note that the specific filename will vary, depending on your version:
Double click on the Install PVS.pkg file to launch the Installer:
This will launch the Tenable PVS Installer, which will walk you through the upgrade process and any required configuration
changes. At any point prior to completion, configuration options may be changed by clicking “Back” to go to the previous
step. Clicking “Cancel” will abort the upgrade process completely.
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The next screen displays the End User License Agreement (EULA). The text of the agreement can be copied and pasted into a
separate document file for reference, saved using the “Save…” button, or it can be printed directly from this interface using
the “Print…” button. You must agree to the license to continue the upgrade process and use PVS.
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Click “Install” to begin the upgrade:
Next, the installation process will ask for authentication for permission to install the software.
The installer will request permission to allow PVS to accept incoming network connections. If this option is denied, PVS will
be installed but will have severely reduced functionality.
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The installation will then be completed.
Immediately after the successful upgrade of PVS, the Installer will automatically launch the Safari browser to allow
configuration of PVS for the environment. When presented with the identity dialog box, click “Continue”.
Once the upgrade process has completed, it is suggested to eject the PVS install volume.
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Initial Installation
This section describes the steps required for an initial installation of PVS on Linux, Mac OS X, and Windows platforms.
Linux Installation
To ensure audit record time stamp consistency between PVS and SecurityCenter, make sure that the underlying
OS makes use of NTP as described in:
http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Deployment_Guide/sectDate_and_Time_Configuration-Command_Line_Configuration-Network_Time_Protocol.html
Unless otherwise noted, all commands are performed as the system’s root user.
Install the PVS software for Red Hat with the following command. Note that the specific filename will vary, depending on
your platform and version:
# rpm -ivh pvs-4.2.0-es6.x86_64.rpm
Preparing...
########################################### [100%]
1:pvs
########################################### [100%]
[*] PVS installation completed.
#
The installation will create the directory /opt/pvs, which initially contains the PVS software, default plugins, and directory
structure.
The following command will start PVS for both Red Hat and CentOS systems:
# service pvs start
Once the service has started, a connection may be made using a web browser by navigating to https://<hostname or
IP address>:8835 to continue configuration of the PVS. For additional details, see the “Initial Configuration of the PVS
Server” section of this document.
Ensure that organizational firewall rules permit access to port 8835 on the PVS server.
The software license agreement for PVS is located in the directory /opt/pvs/var/pvs. It is also available online at:
http://static.tenable.com/prod_docs/Tenable_Passive_Vulnerability_Scanner_4.x_Software_License_Agreement.pdf
Windows Installation
Ensure that the latest version of the Microsoft Visual C++ 2010 Redistributable Package is installed for your
platform prior to PVS software installation.
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Unless otherwise noted, perform all commands as a local administrator user. When UAC is enabled, right click on
the installer program and select “Run as Administrator”.
Prior to installing PVS, ensure that any other programs on the system utilizing WinPcap are stopped.
Install the PVS software for Windows by double-clicking on the .exe file downloaded from Tenable. Note that the specific
filename will vary, depending on your platform and/or version:
This will start the installation process by launching the InstallShield Wizard:
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The InstallShield Wizard will walk you through the installation process and any required configuration. At any point prior to
completion, configuration option can be changed by clicking “Back” to go to the previous step. Clicking “Cancel” will abort the
installation process completely.
The next screen displays the End User License Agreement (EULA). The text of the agreement can be copied and pasted into a
separate document file for reference or it can be printed directly from this interface using the “Print” button. You must agree
to the license to continue the installation process and use the PVS.
Next, the installation process will ask for customer information. The user’s name and company name are used to customize
the installation, but are not related to any configuration options (e.g., for interfacing with SecurityCenter).
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The installation process will then verify the path where the PVS binaries will be installed. Clicking on “Change…” will allow
you to specify a custom path:
User data generated by PVS can be stored in a separate location, as specified in the next installation option. Clicking
“Change…” will allow you to specify an alternate location for user data:
If connecting PVS to SecurityCenter, altering the data path will result in the SecurityCenter not being able to
retrieve reports.
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The final screen of the PVS installation configuration options provides the opportunity to go back to make any edits to
information supplied on previous screens. If all of the configuration options specified are satisfactory, click “Install…” to
complete the PVS installation process.
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Once PVS has been installed, it will determine if WinPcap is already installed on the system. If the current version of
WinPcap is installed and detected, the PVS installation process will ask if you wish to force installation or cancel installation
of WinPcap. If it does not detect WinPcap or detects an older version, a second installer will be launched to install or upgrade
that software:
It is advised to use the provided version of WinPcap or newer. PVS has been designed and tested using the
supplied version of WinPcap.
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You must agree to the WinPcap end-user license agreement in order to complete the installation:
WinPcap can be configured to start during boot time. This is highly recommended as PVS cannot operate if this software is
not running.
Once the license has been agreed to and the configuration option specified, click “Install” to complete the process.
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After WinPcap is installed, the PVS installation process is complete. The user will be returned to the desktop.
As a part of the installation process, a new service is installed called “Tenable PVS Proxy Service”. The service is configured to
start automatically when the server starts. Ether navigate to Services and manually launch the service or restart the system
to start the service.
Once the service has started, a connection may be made using a web browser by navigating to https://<hostname or
IP address>:8835 to continue configuration of the PVS. For additional details, see the “Initial Configuration of the PVS
Server” section of this document.
Ensure that organizational firewall rules permit access to port 8835 on the PVS server.
Mac OS X Installation
Install the PVS software for Mac OS X by double clicking on the .dmg file downloaded from the Tenable Support Portal to
mount the disk image “PVS Install”. Note that the specific filename will vary, depending on your platform and/or version:
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Double click on the Install PVS.pkg file to launch the Installer:
This will launch the Tenable PVS Installer, which will walk you through the installation process and any required
configuration. At any point prior to completion, configuration options may be changed by clicking “Back” to go to the
previous step. Clicking “Cancel” will abort the installation process completely.
The next screen displays the End User License Agreement (EULA). The text of the agreement can be copied and pasted into a
separate document file for reference, saved using the “Save…” button, or it can be printed directly from this interface using
the “Print…” button. You must agree to the license to continue the installation process and use PVS.
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Click “Install” to begin the installation:
Next, the installation process will ask for authentication for permission to install the software.
The installer will request permission to allow PVS to accept incoming network connections. If this option is denied, PVS will
be installed but will have severely reduced functionality.
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The installation will then be completed.
Immediately after the successful installation of PVS, the Installer will automatically launch the Safari browser to allow
configuration of PVS for the environment. When presented with the identity dialog box, click “Continue”.
Once the installation process is complete it is suggested to eject the PVS install volume.
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Starting and Stopping PVS for Mac OS X
The preferred method to start and stop the PVS service on Mac OS X is to use the “PVS Preferences” tab under “System
Preferences”. Once launched, the following window will be displayed. To make changes to any of the states of PVS a root
user or equivalent privileges must be used.
The window displays if the PVS is started or stopped and provides a button to start or stop the service. Additionally, a
checkbox is available to enable or disable PVS from running on system startup.
If there are issues with PVS stopping or starting, the following commands can be issued from terminal to
manually force PVS to stop or start.
To start PVS manually from the command line type:
sudo launchctl load /Library/LaunchDaemons/com.tenablesecurity.pvs-proxy.plist
To stop PVS manually from the command line type:
sudo launchctl unload /Library/LaunchDaemons/com.tenablesecurity.pvs-proxy.plist
Removing PVS
This section describes the steps required to remove PVS from Linux, Mac OS X, and Windows platforms.
Removing PVS for Linux
To remove versions of PVS for Linux, first stop the PVS services with the command “service pvs stop”. You will need to
know what name the PVS is registered as within the RPM database. This name will not be the same as the filename used for
installation. To determine what name the PVS is registered as, run the following command:
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# rpm -qa | grep pvs
This will produce output similar to the following:
pvs-4.2.x-es6.x86_64
For this example, the command to remove the PVS RPM would be:
# rpm -e pvs-4.2.x-es6.x86_64
Some files that are user created and/or modified are not removed with the previous command. To completely remove the
remaining files, run the following command with either sudo root or root privileges:
# rm –rf /opt/pvs
Removing PVS for Windows
To remove PVS, under the Control Panel open “Programs and Features” or “Add or Remove Programs”, depending on the
Windows version. Select “Tenable Passive Vulnerability Scanner” and then click on the “Change/Remove” button. This will
open the InstallShield Wizard. Follow the directions in this wizard to completely remove PVS. If you select “Yes” for the
option of removing all files and folders the PVS program, all files and folders, and its features will be removed from the
system. Selecting “NO” will just remove the PVS program from the machine and leave behind user created files and relevant
file folders. A restart is required after removal to complete the process.
Additionally, the WinPcap program must be removed separately.
Removing PVS for Mac OS X
To remove PVS, first stop the PVS services. Then delete the following directories (including subdirectories) and files as either
sudo root or root privileges using the command line:
rm
rm
rm
rm
/Library/LaunchDaemons/com.tenablesecurity.pvs*
–r /Library/PVS
–r /Library/PreferencePanes/PVS*
–r /Applications/PVS
If you are unfamiliar with Unix command line usage on a Mac OS X system, please contact Tenable Support for
assistance.
Initial Configuration of the PVS Server
After the installation and startup of PVS for Linux, Windows, or Mac OS X is complete, configuring the PVS server follows the
same steps for all platforms.
Begin by connecting to the host using a web browser to the host URL at https://<IP address or hosthame>:8835.
The default username is “admin” and the initial password is “admin”.
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After the initial login, a quick setup process begins. The first step is to change the default admin password. At a minimum, the
new password must be at least 5 characters long, contain one capital letter, one lowercase letter, one digit, and one special
character from the list of [email protected]#$%^&*().
The second step is to enter an Activation Code. An Activation Code is required if the PVS will be acting as a standalone
device. If it is to be managed by SecurityCenter, enter “SecurityCenter” without the quotes in the Activation Code box. If the
PVS is to be registered in an Offline mode, enter “Offline” in the Activation Code box. Once the proper information is
entered, proceed to the next step by clicking the “Next Step” button.
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For more information about installing the Activation Code and performing offline plugin updates, please refer to
the PVS Activation Code Installation document.
The third and final step of the Quick Setup is to define the Monitoring Configuration. On this screen, the Monitored
Network Interfaces are selected from those that PVS has identified. One or more of the defined interfaces may be selected.
The “Monitored Network IP Addresses and Ranges” option determines the IP address ranges that PVS will monitor. The
“Excluded Network IP Addresses and Ranges” option determines the IP address ranges that PVS will not monitor. Both
fields accept IPv4 and/or IPv6 CIDR address definitions. When multiple addresses are used, separate the entries using
commas.
Once the Quick Setup steps are completed, the user is presented with the default “Monitoring” page. Once PVS has started
monitoring traffic, the page will display a list of hosts by using a bar chart that indicates the number of vulnerabilities each
host has, color coded to the severity level.
Using the PVS Interface
The interface for PVS has been tested and works on browsers that support HTML5, including the latest available versions
available at the time of this writing including Microsoft Internet Explorer 9-11 (version 9 being the minimum supported),
Firefox 24 and later, Opera 16 and later, and Google Chrome 30 or later. Other browsers that support HTML5 have been
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reported to work, but have not been fully tested by Tenable. This allows PVS to be placed on networks, monitor traffic, and
have the results provided to users without the need for SecurityCenter or a third party tool to analyze the data.
Once logged into PVS, the user is initially presented with the Monitoring page, which includes several navigation options
across the top.
Navigation
Navigation through the PVS interface starts with the options available across the top menu bar.
The four options are titled Monitoring, Results, Users, and Configuration. The Users and Configuration pages are only
available to Administrator level users. From these pages, all of the primary analysis and maintenance tasks may be
performed. Clicking any of the page names will present the user with that page.
The right side of the menu bar indicates the username of the currently logged in user. Clicking the name will present a dropdown menu with three selections. The first is to change the user’s password (which must contain 5 characters, including at
least one each of a lowercase letter, uppercase letter, digit, and a special character). Information about the PVS version, Web
Server Version, HTML client version, links to support and documentation, and license and feed status can be viewed by
selecting the Help & Support link. Selecting the “Sign Out” link will end the current user’s session.
An additional feature introduced with the PVS HTML client 1.2 is the Notification Center, which is in the shape of a bell and
is found to the far right on the menu bar. The bell icon is a color-coded graphical representation of notifications, errors, and
system information generated by PVS. If no alerts are present or all messages are of an informational level, then the bell icon
will be color-coded to the highest notification level currently in the notification history. The list will retain a maximum of
1,000 alerts and will stop adding more until they are cleared.
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The notification icon will change from blue to red making the user aware that there are error alerts in the notification history.
Each individual notification can be removed by clicking the “X” to the right of the description of each event, or the entire history
can be deleted by clicking the “Clear History” button in the lower right corner of the notification pane.
Notifications are not preserved between sessions. Unread notifications will be removed from the list when the
user logs out.
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Monitoring
The monitoring page provides a centralized view of the vulnerabilities discovered by PVS. From this page, the vulnerabilities
may be viewed in a variety of different ways including by host, vulnerability, application, operating system, and connections.
The results may also be exported to different formats for use in other programs.
Across all of the viewable methods available on the Monitoring page, filter options are available to increase granularity when
viewing results.
The “Sort Hosts” drop-down provides an option to sort the host either by hostname or by the count of severity items found
on the hosts. These sorting options can be displayed in either ascending or descending order.
The Actions drop-down tab allows results to either be exported in Nessus V2 format, CSV format for use in other programs,
HTML for viewing the report in a web browser, or for results to be deleted. For the HTML export option, the exported file may
contain one or more chapters including Hosts Summary, Vulnerabilities by Host, and Vulnerabilities by Plugin. Once the file
type and any applicable options are selected, click the “Export” button to generate and download the report. Large amounts of
data will take longer to export.
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The Filter option text field allows for quick filtering based on entered text for the current view of the Monitoring page. Select
the down arrow on the right of the filter to view a rich selection of options based on discovered vulnerability information to
filter the results based on entered values. Results are displayed based on a match of “Any” or “All” entered fields. The search
field contains example hints when empty, but if an incorrect filter value is entered, the field will display a red border. If values
are still incorrect when applying the filters, a notification will be displayed in the upper right corner of the screen to notify the
user of errors that need to be corrected before filtering can be applied.
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Name
Description
Bugtraq ID
Filter the results of discovered vulnerabilities based on their Bugtraq identification.
CPE
Filter the results of discovered vulnerabilities based on their CPE identifier.
CVE
Filter the results of discovered vulnerabilities based on their CVE identifier.
CVSS Base Score
Filter the results of discovered vulnerabilities based on the base CVSS score as reported
by the vulnerability plugins.
CVSS Temporal Score
Filter the results of discovered vulnerabilities based on the temporal CVSS score as
reported by the vulnerability plugins.
CVSS Temporal Vector
Filter the results of discovered vulnerabilities based on the CVSS temporal vector as
reported by the vulnerability plugins.
CVSS Vector
Filter the results of the discovered vulnerabilities based on the CVSS vector.
Host
Filter the results of the discovered vulnerabilities based on the discovered IP address of
the device.
IAVA ID
Filter the results of the discovered vulnerabilities based on the IAVA ID of the
vulnerability.
IAVB ID
Filter the results of the discovered vulnerabilities based on the IAVB ID of the
vulnerability.
IAVT ID
Filter the results of the discovered vulnerabilities based on the IAVT ID of the
vulnerability.
OSVDB ID
Filter the results of the discovered vulnerabilities based on the discovered OSVDB
identifier.
Plugin Description
Filter the results of the discovered vulnerabilities based on text available in the
description of the vulnerabilities.
Plugin Family
Filter the results of the discovered vulnerabilities based on the family of vulnerabilities
discovered.
Plugin ID
Filter the results of the discovered vulnerabilities based on the plugin ID that identified
the vulnerability.
Plugin Name
Filter the results of the discovered vulnerabilities based on text contained in the name of
the plugin that discovered the vulnerability.
Plugin Output
Filter the results of the discovered vulnerabilities based on text contained in the output
of the plugin that discovered the vulnerability.
Port
Filter the results of the discovered vulnerabilities based on the port the vulnerability was
discovered on.
Protocol
Filter the results of the discovered vulnerabilities based on the detected protocol: tcp,
udp, or icmp.
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Risk Factor
Filter the results of the discovered vulnerabilities based on the identified risk factor.
See Also
Filter the results of the discovered vulnerabilities based on the text available in the “See
Also” field of the plugin.
Solution
Filter the results of the discovered vulnerabilities based on text available in the solution
section of the plugin.
STIG Severity
Filter the results of the discovered vulnerabilities based on STIG severity level in the
plugin.
Synopsis
Filter the results of the discovered vulnerabilities based on text available in the synopsis
section of the plugin.
Hosts Tab
The Hosts tab on the Monitoring page displays a list of the discovered hosts along with a bar chart that is color coded to
indicate the variety of severity levels detected on the host, as well as the total number of each level if there is room to display
it.
Selecting a host from the list will display the vulnerabilities discovered by severity order by default from “Critical” down to
“Informational”. The names of the vulnerability, vulnerability family, and the number discovered will be listed. Selecting any
of these from the list will display vulnerability details including a synopsis, description, solution, plugin information, risk
information, reference information, and affected ports and services for the host. Selecting the “Remove” button will remove
the detected vulnerability from the selected host from the results.
Vulnerabilities Tab
The Vulnerabilities tab provides a list of the vulnerabilities detected by PVS. The initial sort is by severity level from
“Critical” to “Informational”. The vulnerability names are displayed along with the family and the number of detected
vulnerabilities. Selecting any of these from the list will display vulnerability details including a synopsis, description, solution,
plugin information, risk information, reference information, and affected hosts. Selecting an affected host will display the
summary of vulnerabilities for that host. Selecting the “Remove” button will remove the detected vulnerability from the
results.
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Clicking on a vulnerability while on the vulnerability tab the vulnerability can be sorted and filtered by last observed or in
either ascending or descending order based on host IP as shown in the image below.
Applications Tab
The Applications tab provides a list of discovered applications and their affected vulnerabilities. The summary page displays
a list sorted by the highest reported severity and includes the name and the number of discoveries. Selecting a particular
application will present a list of affected hosts. Clicking on a host will display the affected port and protocol, the software and
version, and the service as available.
Operating System Tab
The Operating Systems tab provides a list of discovered operating systems. The summary page lists the severity, operating
system name as detected, and the number of discoveries. Selecting an operating system name from the list will display the
severity, the version of the operating system, and service as available.
Connection Tab
The Connections tab displays the Client Connection Summary list. A list of hosts is displayed and clicking on any of the hosts
provides information on connections from the host to other hosts, which port(s) were used, and the services if known.
Selecting the “Remove” button will remove the detected vulnerability from the results.
Dashboard Tab
The Dashboards tab displays the contents of the vulnerability tab as a graphical layout. The default dashboard layout
displays: Top 10 Hosts, Top 10 Talkers, Top 5 Applications, Top 10 Vulnerabilities, and Distribution by Operating System.
Selecting the “X” button, located in the top right corner of each dashboard component, will temporarily remove the
dashboard from the dashboard tab. Clicking the refresh icon on any individual component will refresh the component,
additionally clicking the large refresh icon located to the top right of the dashboard components can be used to refresh the
entire page.
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Dashboard Vulnerabilities Tab
From this screen a user can use the All Time drop-down to apply filtering based the last 24 hours, last 3 days, last 7 days, last
30 days, all time, or create a custom time frame for filtering.
Dashboard Events Tab
The Events tab displays a graphical representation of the number of maximum viewable realtime events as defined in the
Realtime Events section of the PVS Settings.
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From the Events Tab screen a user can use the Filter Events drop-down to apply filtering for destination host, destination
port, event name, plugin ID, source host, or source port. With the option to have the filter either match any or all of the filters
created, these filters can also be applied to match, not match, contain, or not contain the input from the user.
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Results
The Results page contains snapshots of the monitored data, results from PCAP files entered manually via the command line
or the client GUI, and uploaded PVS reports. The Monitored Data snapshots are generated regularly based on the Report
Frequency setting. They are stored until deleted or the Report Lifetime setting is put into effect. When a result grouping is
selected, it may be viewed using the same analysis tools described in the previous Monitoring section.
Additionally, by checking the desired Snapshot results and then using the Diff Snapshots option from the Actions drop-down,
two or more snapshots may be compared as shown in the example below:
Users
The Users screen provides a list of the available users on the PVS server. This screen is only available to Administrator level
users. User accounts may be managed from this screen. The list includes a user’s login ID, date of last login, and a true/false
message indicating if the account is an administrator or not. Hovering over a user account will display an “x” on the right hand
side. When clicked, a dialog box opens asking to confirm the deletion of the user. Logged in users may not delete their own
account. Multiple users may be selected using the checkboxes on the left side of the “Name” list. Checking any of these boxes
will cause a new “Actions” menu to appear to the left of the “New User” menu allowing the user to select “Delete User” from
the Actions drop-down menu.
Creating Users
A new user may be created by clicking the “New User” button. A dialog box will open and prompt for the new user’s
information. The username is case sensitive and the password must conform to the minimal PVS password policy. Selecting
the Administrator checkbox will create the user with those rights.
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When users are created which will authenticate with SSL Client Certificates, the user name must match the
Common Name in the certificate.
Selecting a user from the list of existing users will open an Edit User dialog box. This allows for changing the user’s password
and the user’s Administrator status.
Resetting User Passwords
When a user has forgotten their password user passwords can be reset by an account with administrative privileges. This is
performed via the GUI by clicking the username, which launches the Edit User screen.
Additionally user accounts can have their password reset via command line interface by issuing the appropriate command
for your operating system from the pvs binary directory.
# ./pvs --users --chpasswd admin
Resetting Locked Accounts
Linux and Mac OS X
If a user has been locked out, user accounts can be unlocked by an account with administrative privileges. This can be
performed via command line interface on Linux and Mac OS X operating systems by issuing the command:
# -rm /opt/pvs/var/pvs/users/<locked account name>/hash.lockedout
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Once this file has been removed the admin account can then follow the steps defined in the previous section to reset the
user’s password if needed.
Windows
If a user has been locked out, user accounts can be unlocked by an account with administrative privileges. This can be
performed via command line interface on Windows operating system by issuing the command:
del C:\ProgramData\Tenable\PVS\pvs\users\<locked_account_name>\hash.lockedout
Alternatively, the admin can navigate to this directory and manually delete the hash.lockedout file.
Configuration
The Configuration page allows Administrator level users to configure PVS for the local environment. There are five tabs
available: PVS Settings, Feed Settings, Web Proxy Settings, Chart Settings, and Plugin Settings.
PVS Settings Tab
The PVS Settings tab provides options for configuring the network settings for PVS. This is the main configuration page that
controls what network(s) are monitored or excluded, how to monitor the network, and what network interfaces PVS has
identified for monitoring.
When options are changed on this page and submitted, the PVS service on the host must be stopped and started
for them to take effect.
Name
Description
ACAS Classification
ACAS
Support for ACAS banners may be enabled from the command line of the PVS server
service using the command ./pvs --config --add "ACAS Classification"
"SECRET" from the binary directory on the server and is case sensitive. “SECRET” may
be replaced by "UNCLASSIFIED","CONFIDENTIAL","TOP SECRET", or "NOFORN".
Once enabled, a drop-down selection for the ACAS option will appear in the GUI front
end.
Support for ACAS banners may be disabled from the command line of the PVS server
using the command ./pvs --config --delete "ACAS Classification" from
the binary directory on the server and is case sensitive.
Advanced
Login Banner
Provides a text box used in the creation of login banners.
Memory
Sessions Cache Size
The Sessions Cache Size is the size in megabytes (MB) of the session table. Adjust the
session size as needed for the local network.
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Packet Cache Size
The Packet Cache Size keyword specifies the maximum size in megabytes of the cache
that will be used to store the contents of the packets collected before processing. By
default it is set to 512 MB with a maximum size of 512 MB. When the cache is full, any
subsequent packets captured will be dropped until space in the cache becomes available.
Monitoring
Monitored Network
Interfaces
The Monitored Network Interfaces field specifies the network device(s) to use for
sniffing packets. Devices may be selected individually or in multiples. At least one
interface must be selected from the list of available devices.
Monitored Network IP
Addresses and Ranges
Specifies the network(s) to be monitored. The default setting is to monitor all IPv4
addresses with the setting of 0.0.0.0/0. This should be changed to only monitor target
networks; otherwise PVS may quickly become overwhelmed. It may contain both IPv4
and IPv6 addresses. Multiple addresses are separated by commas. When monitoring
VLAN networks, a syntax of “vlan ipaddress/subnet” must be used. Example:
192.168.1.0/24,2001:DB8::/64,10.2.3.0/22,vlan 172.16.0.0/16,192.168.3.123/32
Excluded Network IP
Addresses and Ranges
Specifies any network(s) to specifically exclude from PVS monitoring. Specify networks
using CIDR notation. It may contain both IPv4 and IPv6 addresses. Multiple addresses
are separated by commas. When excluding VLAN networks a syntax of “vlan
ipaddress/subnet” must be used. If left blank, no addresses will be excluded.
Example: 192.168.1.0/24,2001:DB8::/64,10.2.3.0/22,vlan
172.16.0.0/16,192.168.3.123/32
PVS Proxy
PVS Proxy Username
This configures the username that SecurityCenter 4.7.x or earlier will use to connect to the
PVS proxy.
PVS Proxy Password
The PVS proxy password is the password that SecurityCenter 4.7.x or earlier will use in
combination with the username to connect to the PVS proxy.
PVS Proxy IP Address
By default, the PVS proxy listens on all IPv4 addresses with the setting of 0.0.0.0. This
may be configured to listen on a specific IPv4 address. The PVS proxy only listens on the
configured address if configured for SecurityCenter 4.7.x or earlier connectivity.
PVS Proxy Port
This setting configures the PVS proxy listening port. By default it is set to 1243 and may
be altered as appropriate for the local environment. The PVS proxy only listens on the
configured port if configured for SecurityCenter 4.7.x or earlier connectivity.
PVS Restart Attempts
The PVS proxy monitors the state of the PVS engine. If the engine stops running, the
proxy will attempt to restart the PVS engine the specified number of times, with the
default setting being 3 and may be set to a value of 1 to 9. Once the restart attempt limit
is reached, it will stop trying for a period of 30 minutes.
PVS Restart Interval
This setting configures the amount of time, in minutes, between PVS restart attempts.
This setting is set to 10 minutes by default and may be set to a value of 1 to 3600.
PVS Web Server
Enable SSL for Web Server
PVS enables SSL protection for connections to the web server by default. Disabling this
option will send traffic between a web browser and PVS unencrypted and is therefore
not recommended. Custom SSL certificates may be installed in the
/opt/pvs/var/pvs-proxy/ssl directory. Changes to this setting require that the
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PVS services be stopped and started.
Minimum Password Length
The Minimum Password Length option determines the lowest number of characters a
password may contain. This may be between 5 and 32 characters, with a default setting
of 5.
PVS Web Server Address
By default the PVS web server listens on all available IPv4 and IPv6 addresses utilizing
the setting 0.0.0.0. This may be changed to listen on a specific address or multiple
addresses separated by commas.
PVS Web Server Port
This is the port the PVS web server listens on, which by default is 8835. This may be
altered as appropriate for the local environment.
PVS Web Server Idle Session
Timeout
This setting is the number of minutes after which a web session becomes idle. The
default setting for this timeout is 30 minutes. The valid settings are between 5 and 60
minutes.
Enable SSL Client Certificate
Authentication
When selected, the web server will only accept SSL client certificates for user
authentication.
Enable Debug Logging for
PVS Web Server
When selected, debug information will be included in the web server logs for
troubleshooting issues related to the web server. The logs will grow rather large if this is
routinely enabled.
Maximum User Login
Attempts
Denotes the number of attempts a user can make when entering an incorrect password
before the user’s account is locked out.
Max Sessions per User
Limits the number of concurrent sessions that a user can have running at any one time.
Enforce Complex Passwords
When selected, this forces the user’s passwords to contain at least one uppercase
character, one lower case character, one digit, and one special character [email protected]#$%^&*()
Plugins
Process High Speed Plugins
Only
PVS is designed to expect to find various protocols on non-standard ports. For example,
PVS can easily find an Apache server running on a port other than 80. However, on a high
traffic network, PVS can be placed into a “high-speed” mode that allows it to focus certain
plugins on specific ports. When the high speed option is enabled, any plugin that utilizes
the keywords hs_dport or hs_sport will be executed only on traffic traversing the
specified ports.
Enable Automatic Plugin
Updates
When enabled, PVS will automatically update its plugins from the Tenable site on a daily
basis. Disabling this option if the PVS server is not connected to the Internet is
recommended.
When the HTML Client is updated the web browser needs to be refreshed
to utilize the new client. In some cases the browser’s cache must be deleted
to view the new client.
Realtime Events
Realtime Events File Size
The Realtime Events File Size option specifies the maximum amount of data from
realtime events that will be stored in one text file. The option must be specified in
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kilobytes, megabytes, or gigabytes by appending a “K”, “M”, or “G” to the value.
Log Realtime Events
This option records PVS detected realtime events to a local log file.
Enable Realtime Event
Analysis
When checked, this option enables PVS to analyze realtime events.
Maximum Viewable Realtime
Events
Denotes the number of events that will be viewable at any given time.
Reports
Report Threshold
This setting is used to determine the number of times the encryption detection algorithm
is executed during a session. Once the threshold is reached, the algorithm is no longer
executed during the session. This variable has a default of “3”.
Report Lifetime
Reports can be cached for a specified number of days. After the configured day count is
met, PVS’s entire model of a discovered network is completely removed. PVS starts over
again learning about the hosts that are involved on the network. This value can be set to a
maximum value of 90 days, if this behavior is not desired. However, it is very useful to have
fresh reports on a weekly or monthly basis. The default value is 7 days.
Report Frequency
This variable specifies in minutes (default 15) how often the PVS will write a report.
SecurityCenter 4.6 and higher will retrieve the PVS report every 15 minutes.
Knowledgebase Lifetime
The maximum length of time in seconds that a knowledgebase entry remains valid after
its addition.
New Asset Discovery Interval
PVS listens to network traffic and attempts to discover when a new host has been added.
To do this, the PVS constantly compares a list of hosts that have generated traffic in the
past to those currently generating traffic. If it finds a new host generating traffic, it will
issue a “new host alert” via the realtime log. For large networks, PVS can be configured to
run for several days to gain knowledge about which hosts are active. This prevents PVS
from issuing an alert for hosts that already exist. The number of days PVS should monitor
traffic to learn which hosts are active is specified by this setting. For large networks,
Tenable recommends that PVS operate for at least two days (the default setting) before
detecting new hosts.
Connections to Services
When enabled, this option enables PVS to log which clients are attempting to connect to
servers on the network and what port they are attempting to connect to. They do not
indicate if the connection was successful, but only indicate that an attempt to connect
was made. Events detected by PVS of this type are logged as PVS ID “00002”.
Show Connections
When enabled, PVS will record clients in the focus network that attempt to connect to a
server IP address and port and receive a positive response from the server. The record will
contain the client IP address, the server IP address, and the server port that the client was
attempting to connect to. For example, if four different hosts within the focus network
attempted to connect with a server IP over port 80 and received a positive response, then
a list of those hosts would be reported under event “00003” and port 80.
Session Analysis
Encrypted Sessions
Dependency Plugins
This list of Plugin IDs, separated by commas, is used to detect encrypted traffic.
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Encrypted Sessions Excluded
Network Ranges
This setting defines the list of IPv4 and IPv6 addresses and ports in CIDR notation to be
excluded from monitoring for encrypted traffic. Example:
192.168.1.0/24,2001:DB8::/64,10.2.3.0/22,vlan 172.16.0.0/16,192.168.3.123/32
Interactive Sessions
Dependency Plugins
This list of Plugin IDs, separated by commas, is used to detect interactive sessions.
Interactive Sessions Excluded
Network Ranges
This setting defines the list of IPv4 and IPv6 addresses and ports in CIDR notation to be
excluded from monitoring for interactive sessions. Example:
192.168.1.0/24,2001:DB8::/64,10.2.3.0/22,vlan 172.16.0.0/16,192.168.3.123/32
Syslog
Realtime Syslog Server List
Specifies the IPv4 or IPv6 address and port of a Syslog server to receive realtime events
from the PVS. This setting has the ability to add, edit, or remove addresses syslog
addresses used by PVS. A local Syslog daemon is not required. Syslog items can be
specified to either Standard or CEF formats as well as UDP or TCP protocols. Example:
192.168.1.12:4567,10.10.10.10:514,[2001:DB8::23B4]:514
Vulnerability Syslog Server
List
Specifies the IPv4 or IPv6 address and port of a Syslog server to receive vulnerability
data from PVS. This setting has the ability to add, edit, or remove addresses syslog
addresses used by PVS. A local Syslog daemon is not required. Syslog items can be
specified to either Standard or CEF formats as well as UDP or TCP protocols. Example:
192.168.1.12:4567,10.10.10.10:514,[2001:DB8::23B4]:514
While PVS may display multiple log events related to one connection, it will
only send a single event to the remote Syslog server(s).
Feed Settings Tab
The Feed Settings tab allows for updating the Activation Code, plugins, performing offline updates, and configuring a custom
plugin feed host.
The Activation Code and manual plugin update buttons are only used when using PVS in a stand-alone mode (not attached to
a SecurityCenter). The Activation Code will only need to be updated when it expires. When PVS is used with SecurityCenter,
entering “SecurityCenter” in the Activation Code box will enable PVS to work with SecurityCenter installations.
The Offline Update allows for manually updating the plugins when the PVS host is not able to connect to the Internet. After
downloading the plugin update archive from Tenable, select the “Choose File” button and select the archive to upload. Click
the “Upload Archive” button to send the file to the PVS host, which will then update the plugins. If a new client is part of the
update, the browser needs to be refreshed to view the updated client.
The Custom Plugin Feed host is an alternate feed host. These are typically hosted on a local network to provide custom PVS
plugins.
Web Proxy Settings Tab
The Web Proxy Settings tab configures the settings for a web proxy if one is needed for plugin updates. These settings
include the proxy host IP address, port, username, password, and a user-agent field if a custom agent string is needed.
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Chart Settings Tab
The Chart Settings tab configures the settings for the dashboard tab of the monitoring page. The Chart Settings tab lists the
five default charts displayed on the dashboard tab.
The Chart Settings tab allows the user to deselect any unwanted chart from the dashboard tab. The Chart Settings tab also
gives the user the option to create a simple custom chart based on: chart type, Dashboard Family, Category, Filters, and
Viewable.
Creating a Custom Chart
From the Chart Settings Tab click the Create Chart button located at the upper right of the Chart Settings Tab. This will
bring up the chart template as shown below.
1.
From this screen add a name for the chart, a description of what the chart will be displaying, and then select what
kind of chart is to be created, either a pie or bar chart.
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For this example we are creating a dashboard to display the top vulnerabilities from machines who are reporting to
have BitTorrent activity associated with them.
2.
Click the next tab, Dashboard Family. This will enable you to enter a value that represents the number of items
returned for this chart ranging from 1 to 20.
After selecting the number of items to be displayed on the chart, click on the text “Top” to have this value added to
the Current Chart Query.
3.
Selecting the Category tab will bring up the screen to choose what type of items will be displayed on the chart such
as: hosts, vulnerabilities, applications, operating systems, or connections.
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4.
Selecting the tab labeled Filter will bring up the option to filter the results based on any filters created for the chart.
After selecting the filter rules, click the + icon to apply the rule to the chart.
For this example, a filter based on the Plugin ID of 3920 was created, which triggers when BitTorrent client activity
is detected.
5.
The last tab to check is the Viewable tab, which enables the chart as viewable on the main Dashboard.
Once these steps have been completed, the custom chart will now be viewable by selecting the monitoring tab and then
selecting the dashboard tab.
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Plugin Settings Tab
The Plugin Settings tab allows the user to disable or enable any plugins, disable or enable any PASLs, and also allows the user
to create a custom plugin.
Enable/Disable Plugins Action Screen
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Enable/Disable PASLs Action Screen
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Create Plugin Action Screen
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Additionally to the basic and advanced plugin fields that have been provided, there is also the option for the user to create a
new plugin field by clicking the Add Plugin Field button on the top right of the Plugin Settings tab while Create Plugin has
been selected.
Custom Plugin Field
Purpose
ID
Numeric ID of the plugin
Name
Title of the plugin
Description
Full text description of the vulnerability
Synopsis
Brief description of the plugin or vulnerability
Solution
Remediation information for the vulnerability
See Also
External references to additional information regarding the vulnerability
Risk
Info, Low, Medium, High, or Critical risk factor
Plugin Output
Actual text output of the Nessus scanner
Family
Family the plugin belongs to
Dependency
Other dependencies required to trigger the custom plugin
NoPlugin
This keyword will prevent a plugin from being evaluated if another plugin has already
matched. For example, it may make sense to write a plugin that looks for a specific
anonymous FTP vulnerability, but have it disabled if another plugin that checked for
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anonymous FTP had already failed.
No Output
For plugins that are written specifically to be used as part of a dependency with another
plugin, the “nooutput” keyword will cause the PVS to not report anything for any plugin
with this keyword enabled.
Client Issue
Indicates the vulnerability is located on the client side
Plugin Type
Used to denote a plugin type of vuln, Realtime, Realtimeonly
cve
CVE reference
bid
Bugtraq ID (BID) reference
osvdb
External reference (e.g., OSVDB, Secunia, MS Advisory)
nid
To track compatibility with the Nessus vulnerability scanner, Tenable has attempted to
associate PVS vulnerability checks with relevant Nessus vulnerability checks. Multiple
Nessus IDs can be listed under one “nid” entry such as “nid=10222,10223”.
cpe
Filter the results of discovered vulnerabilities based on their CPE identifier
Match
This keyword specifies a set of one or more simple ASCII patterns that must be present
in order for the more complex pattern analysis to take place. The “match” keyword gives
PVS a lot of its performance and functionality.
Regex
This keyword specifies a complex regular expression search rule that will be applied to
the network session.
Revision
Revision number associated with custom plugin
Raw Text Preview
A preview of the custom plugin in raw text.
Example of a custom plugin created to find a IMAP Banner of Tenable Rocks:
id=79000
name=IMAP Banner
description=An IMAP server is running on this port. Its banner
is Tenable Rocks
risk=NONE
match=OK
match=IMAP
match=server ready
regex=^.*OK.*IMAP.*Tenable Rocks
Command Line Operation
The PVS engine provides many options to update and configure PVS from the command line in both Windows and Linux
versions. The HTML5 interface is considered the primary method to make changes. When using the command line interface in
Linux, it is assumed the commands are being performed by a root user or equivalent. When the command line is used in
Microsoft Windows, it is assumed that the shell has been launched using the “Run as Administrator” or an equivalent option.
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This section is separated into three sections: a section each for Windows, Linux, and Mac OS X specific command line options
and a section for common options.
Command Line Operations for Linux
Starting the Passive Vulnerability Scanner for Linux
The service command is the preferred method to launch the pvs and pvs-proxy binaries as follows:
# service pvs start
Starting PVS
Starting PVS Proxy
# ps aux|grep pvs
root
18626 9.5 70.5 1492840 1357176 pts/3 Sl
root
18629 0.2 0.2 21160 4892 pts/3
S
proxy
[
[
15:38
15:38
OK
OK
]
]
0:03 /opt/pvs//bin/pvs
0:00 /opt/pvs//bin/pvs-
Once running, the pvs binary will be monitored by the pvs-proxy daemon utilizing its watchdog options.
In this mode, the PVS will store its vulnerability reports in a directory monitored by the PVS Proxy. When the SecurityCenter
connects to the PVS Proxy, it will copy the appropriate report found in this directory to the SecurityCenter and import it into
the relevant databases.
Once a day, as scheduled, if the SecurityCenter has received new passive vulnerability plugins from Tenable, it will install
them in the PVS plugin directory. PVS will detect the change and automatically reload and begin using the new plugins.
Realtime PVS data will be communicated to the configured Log Correlation Engine server or syslog server(s) in realtime.
Stopping the Passive Vulnerability Scanner for Linux
If you need to stop the PVS service for any reason, use the following command for PVS for Red Hat and CentOS:
# service pvs stop
Stopping PVS Proxy
Stopping PVS
[
[
OK
OK
]
]
[
[
[
[
OK
OK
OK
OK
]
]
]
]
Or to restart the service, use the command:
# service pvs restart
Stopping PVS Proxy
Stopping PVS
Starting PVS
Starting PVS Proxy
File Locations
PVS installs its files into the following locations:
Path
Purpose
/opt/pvs
Base directory
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/opt/pvs/bin
Location of the PVS and PVS Proxy executables, plus several helper tools for the PVS
Proxy daemon
/opt/pvs/var
Contains the folders for PVS and the PVS-Proxy
/opt/pvs/var/pvs
Plugins, discovered vulnerabilities, log files, keys, software license agreement, and other
miscellaneous items among its directories and sub-directories
db
This directory contains the database files relating to the configuration, reports, and users
for PVS.
kb
This directory stores the PVS knowledgebase, if used.
logs
Contains PVS logs
plugins
Contains the tenable_plugins.prmx pushed down by SecurityCenter. May also
contain custom plugins.
Do not change from the default of
C:\ProgramData\Tenable\PVS\pvs if SecurityCenter is being used
to manage the plugins.
pvs-services
A file that PVS uses to map service names to ports. This file may be edited by the user.
Plugin updates will not overwrite modifications to the file.
reports
Contains reports generated by PVS with the exception of .nsr. This folder contains the
.nessus file generated by default.
scripts
Folder for custom scripts, if any
users
Contains folders for user files and reports
www
Contains the files for the PVS web front-end
/opt/pvs/var/pvs-proxy
Parent folder for files used/created by the PVS proxy
logs
Contains PVS proxy and PVS proxy service logs
scans
By default, PVS creates the .nsr file in the scans directory. The proxy is then
responsible for handing the report to SecurityCenter when SecurityCenter attempts to
pull it.
ssl
Contains SSL certificates used by the proxy and web server for the SSL connection
between itself and SecurityCenter or the web browser
Command Line Operations for Windows
This section describes some operations that are performed on the PVS server from a command line in Windows. Command
line operations need to be executed from a Windows shell that has been launched using the “Run as Administrator”
command or similar, depending on the Windows version.
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File Locations
PVS installs its files into the following locations:
Path
Purpose
C:\Program Files\Tenable\PVS
Contains PVS binaries and dependent libraries
C:\ProgramData\Tenable\PVS
Contains all data files consumed and output by PVS and PVS Proxy (i.e.,
configuration, plugins, logs, reports)
The following is the folder layout under C:\ProgramData\Tenable\PVS\:
Folder
Purpose
pvs
Parent folder for PVS logs, reports, plugins, and scripts directories. Also contains the
pvs-services file.
db
This directory contains the database files relating to the configuration, reports, and users
for PVS.
kb
This directory stores the PVS knowledgebase, if used.
logs
Contains PVS logs
plugins
Contains the tenable_plugins.prmx pushed down by SecurityCenter. May also
contain custom plugins.
Do not change from the default of
C:\ProgramData\Tenable\PVS\pvs if SecurityCenter is being used
to manage the plugins.
pvs-services
A file that PVS uses to map service names to ports. This file may be edited by the user.
Plugin updates will not overwrite modifications to the file.
reports
Contains reports generated by PVS with the exception of .nsr. This folder contains the
.nessus file generated by default.
scripts
Folder for custom scripts, if any
users
Contains folders for user files and reports
www
Contains the files for the PVS web front-end
pvs-proxy
Parent folder for files used/created by the PVS proxy
logs
Contains PVS proxy and PVS proxy service logs
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scans
By default, PVS creates the .nsr file in the scans folder. The proxy is then responsible
for handing the report to SecurityCenter when SecurityCenter attempts to pull it.
ssl
Contains SSL certificates used by the proxy and web server for the SSL connection
between itself and SecurityCenter or the web browser
run
Contains process ID temporary files
Starting and Stopping PVS
PVS is controlled as a service under Windows. To start or stop PVS, launch the Services control panel utility. Under the list of
services find “Tenable PVS Proxy Service”. Right clicking on the service will provide a list of options for the service, including
the ability to start or stop the Tenable PVS or Tenable PVS Proxy service.
Command Line Operations for Mac OS X
Stopping the Passive Vulnerability Scanner for Mac OS X
After the installation, the PVS service will start. During each reboot, the service will automatically start. If there is a reason to
start or stop the service, it can be done via a Terminal window (command line). If performed via the command line, it must be
run as “root”, or via sudo:
Action
Command to Manage PVS
Start
# launchctl load -w /Library/LaunchDaemons/com.tenablesecurity.pvs-proxy.plist
Stop
# launchctl unload -w /Library/LaunchDaemons/com.tenablesecurity.pvs-proxy.plist
Alternately, the PVS service can be managed via System Preferences.
File Locations
PVS installs its files into the following locations:
Path
Purpose
/Library/PVS
Base directory
/Library/PVS/docs
This directory contains the PVS license agreement in various file formats.
/Library/PVS/bin
Location of the PVS and PVS Proxy executables, plus several helper tools for the
PVS Proxy daemon
/Library/PVS/var/pvs
Plugins, discovered vulnerabilities, log files, keys, software license agreement, and
other miscellaneous items among its directories and sub-directories
db
This directory contains the database files relating to the configuration, reports, and
users for PVS.
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kb
This directory stores the PVS knowledgebase, if used.
logs
Contains PVS logs
plugins
Contains the tenable_plugins.prmx pushed down by SecurityCenter. May
also contain custom plugins.
Do not change from the default of
C:\ProgramData\Tenable\PVS\pvs if SecurityCenter is being
used to manage the plugins.
pvs-services
A file that PVS uses to map service names to ports. This file may be edited by the
user. Plugin updates will not overwrite modifications to the file.
reports
Contains reports generated by PVS with the exception of .nsr. This folder
contains the .nessus file generated by default.
scripts
Folder for custom scripts, if any
users
Contains files and reports for the PVS users.
www
Contains the files for the PVS web front-end
/Library/PVS/var/pvs-proxy
Parent folder for files used/created by the PVS proxy
logs
Contains PVS proxy and PVS proxy service logs
scans
By default, PVS creates the .nsr file in the scans folder. The proxy is then
responsible for handing the report to SecurityCenter when SecurityCenter
attempts to pull it.
ssl
Contains SSL certificates used by the proxy and web server for the SSL connection
between itself and SecurityCenter or the web browser
Common Command Line Options
PVS may be run from the command line to analyze pcap files and generate a report file for use with SecurityCenter or other
programs, update plugins, and perform configuration tasks. The following is a list of options available and their purpose.
Running the PVS binary with the –h option will display a list of available options.
When using the PVS binary at the command line to perform tasks or change options, the PVS services need to be
stopped. Failure to do so may result in undesired results in the performance of the command line task or the PVS
monitoring.
The PVS binary for Windows is located at:
C:\Program Files\Tenable\PVS>pvs.exe
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The PVS binary for Mac OS X is located at:
# /Library/PVS/bin
The PVS binary for Linux is located at:
# /opt/pvs/bin/pvs
Running the pvs command on Linux without specifying the full path will result in launching the Linux pvs (physical
disk volume) tool rather than the Tenable Passive Vulnerability Scanner.
Option
Purpose
-m
Shows various aspects of memory usage during the processing of the pvs command.
-p packet_dump_file
Replace packet_dump_file with the local file name or path to file name to write out
the captured packets to a file.
-f packet_dump_file
Replace packet_dump_file with the path to the pcap file you wish to have pvs
process.
-h
Displays the command line options help file.
-a <activation code>
Enter the Activation Code to activate the PVS to enable plugin updates and monitoring
functions.
-l
Displays a list of the plugin IDs that are loaded by the PVS.
-v
Shows the version information about the installed PVS.
-d debug mode
This command allows PVS to run in debug mode for troubleshooting purposes
It is important to note that with PVS operating with this option enabled will
result in more resources used by the system and should only be used when
directed by a Tenable Support Technician.
--config --list
Lists the current PVS and PVS Proxy configuration parameters. Parameter values are
listed to the left of the colon character and are case sensitive. The value of the parameter
is displayed to the right of the colon character.
--config --add
"custom_paramater
name" "parameter
value"
Add a custom configuration parameter for PVS or PVS Proxy. The double quote
characters are required, and single quotes may be used when special characters are
required.
--config "parameter
name" ["parameter
value"]
Displays the defined parameter value. If a value is added at the end of the command, the
parameter is updated with the new setting. The double quote characters are required,
and single quotes may be used when special characters are required.
--config --delete
"custom_parameter
name"
The delete command may be used to remove custom configuration parameters.
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--register-offline
<.rc file>
When using PVS in an offline mode, the .rc file obtained from Tenable is used in this
command.
-- challenge
When using PVS in an offline mode, a challenge code is required by Tenable to generate
the proper .rc file. This command provides the required challenge code.
--update-plugins
<plugins tarball>
When using the PVS in an offline mode, updating the plugins requires downloading a
tarball from Tenable. When updating the plugins from the command line, this command
is used to identify the file to use for updating the plugins.
pvs --users --add
This command is used to add a new user to PVS with the expected values of: ["username"
"password" admin]: add new user. Expected values for “admin” flag are: 1 - grant user
administrator level privileges or 0 - don’t grant user administrator level privileges.
pvs --users --delete
Used to remove a user from PVS.
pvs --users --chpasswd
Used to change the password for a PVS user.
Define Unknown or Customized Ports
Many networks will contain traffic on ports PVS has defined as a different traffic type or on alternate ports. If the port is not
defined at all it will be displayed as “Unknown”. The pvs-services file may be edited to customize or add the port
information to provide accurate reporting for the ports on the network.
For example, there are two lines in the pvs-services file by default that define SMTP traffic. They read “smtp
25/tcp” and “smtp
25/udp”. If the organization routinely sends SMTP data over port 2525 those lines can be changed
to or have lines added to the file that reads “smtp
2525/tcp” and “smtp
2525/udp”.
PVS Realtime Traffic Analysis Configuration Theory
This section describes how configuration options affect PVS operation and provides details on PVS architecture.
Focus Network
When a focus network is specified via the “networks” keyword, only one side of a session needs to be matched on the list. For
example, if you have a DMZ that is part of the focus network list, the PVS will report on vulnerabilities of the web server
there, but not on web clients visiting from outside the network. However, a web browser within the DMZ visiting the same
web server would be reported.
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In the above picture, three sessions labeled A, B, and C are shown communicating to, from, and inside a focus network. In
session A, the PVS only analyzes vulnerabilities observed on the server inside the focus network and does not report client
side vulnerabilities. In session B, the PVS ignores vulnerabilities on the destination server, but reports client side
vulnerabilities. In session C, both client and server vulnerabilities are reported.
There is one more filter that the PVS uses while looking for unique sessions. This is a dependency that requires the host to be
running a major service. These dependencies are defined by a list of PVS plugin IDs that identify SSL, FTP and several dozen
other services.
Finally, the entire process of detecting these sessions can be filtered by specific network ranges and ports. For example, if a
University ran a public FTP server that had thousands of downloads each hour, it would make sense to disable interactive
sessions on port 21 on that FTP server. Similarly, disabling encryption detection on ports such as 22 and 443 will also
eliminate some noise for the PVS.
Detecting Server and Client Ports
The method used by TCP connections to initiate communication is known as the “three-way handshake”. This method can be
compared to how a common telephone conversation is initiated. If Bob calls Alice, he has effectively sent her a “SYN” packet,
in TCP terms. She may or may not answer. If Alice answers, she has effectively sent a “SYN-ACK” packet. The communication
is still not established, since Bob may have hung up as she was answering. The communication is established when Bob
replies to Alice, sending her an “ACK”.
The PVS configuration option “connections to services” enables PVS to log network client to server activity.
Whenever a system within the monitored network range tries to connect to a server over TCP, the connecting system will
emit a TCP “SYN” packet. If the port the client is connecting on is open, then the server will respond with a TCP “SYN/ACK”
packet. At this point, PVS will record both the client address and the server port the client is connecting to. If the port on the
server is not open, then the server will not respond with a TCP “SYN/ACK” packet. In this case, since PVS never sees a TCP
“SYN/ACK” response from the server, PVS will not record the fact that the client tried to connect to the server port, since the
port is not available to that client.
The “connections-to-services” option does not track how many times the connection was made. If the same host
browses the same web server a million times, or browses a million different web servers once, the host will still be marked as
having browsed on port 80. This data is logged as Nessus ID #00002.
The PVS detects many applications through plugin and protocol analysis. At a lower level, the PVS also detects open ports
and outbound ports in use on the monitored networks. By default, the PVS will detect any TCP server on the protected
network if it sees a TCP “SYN-ACK” packet.
In combination, the detection of server ports and client destination ports allows a network administrator to see who on their
network is serving a particular protocol and who on their network is speaking that protocol.
Detecting Specific Server and Client Port Usage
Another PVS configuration option provides more specific details about server and client port usage. This is the “showconnections” keyword on the configuration page. This setting keeps track of host communication within the focus
network. When the “show-connections” option is enabled, every time a host connects to another host, PVS records the
client, server, and server port, if one of the hosts is in the defined focus network. It does not track the frequency or time
stamp of the connections – just that a connection was made.
The “show-connections” option provides a greater level of detail than the “connections-to-services” option. For
example, if your IPv4 address is 1.1.1.1 or your IPv6 address is 2001:DB8::AE59:3FC2 and you use the SSH service to
connect to “some_company.com”, use of these options would record the following:
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show-connections:
 some_company.com:SSH
2001:DB8::AE59:3FC2 -> some_company.com
connections-to-services
 SSH
2001:DB8::AE59:3FC2 -> SSH
Using the “connections-to-services” option lets you know that the system at 1.1.1.1 and 2001:DB8::AE59:3FC2 uses
the SSH protocol. This information may be useful to know regardless of where the service is being used.
The PVS does not log a session-by-session list of communications. Instead, it logs the relationship between the systems. For
example, if system A is detected using the SSH protocol on port 22 connecting to system B, and both systems are within the
focus network, the PVS would log:

System A browses on port 22

System B offers a service (listens) on port 22

System A communicates with System B on port 22
If system B were outside of the focus network, the PVS would not record anything about the service System B offers, and
would also log that System A browses outside of the focus network on port 22. The PVS does not log how often a connection
occurs, only that it occurred at least once. For connections outside of the focus network, the PVS will only log what ports are
browsed, not the actual destinations.
If logging session-by-session network events is a requirement for your network analysis, Tenable offers the Log
Correlation Engine product, which can be used to log firewall, web server, router, and sniffer logs. For more
information, please visit http://www.tenable.com/products/log-correlation-engine.
What this Means for Firewall Rules
If the PVS is placed immediately behind a firewall, such that all of the traffic presented to the PVS is flowing through the
firewall, then the list of served ports and client side ports and the respective IP addresses of the users is readily available. By
using tools such as SecurityCenter’s Vulnerability Analysis interface, information about these ports (both client and server)
can be browsed, sorted, and reported on. Lists of IP addresses and networks using these client and server ports can also be
viewed.
Working with the SecurityCenter
When multiple PVS sensors are managed by a SecurityCenter, users of the SecurityCenter are able to analyze the aggregate
types of open ports, browsed ports, and communication activity occurring on the focus network. Since the SecurityCenter
has several different types of users and privileges, many different IT and network engineering accounts can be created
across an enterprise so they can share and benefit from the information detected by the PVS.
Selecting Rule Libraries and Filtering Rules
Tenable ships an encrypted library of passive vulnerability detection scripts. This file cannot be modified by the end users of the
PVS. However, if certain scripts need to be disabled, they can be specified by the PASL ID and “.pasl” appended, such as
“1234.pasl”, to disable the PASL with the ID of 1234 on a single line in the disabled-scripts.txt file.
If a plugin needs to be disabled, enter its ID on a single line in the disabled-plugins.txt file. If a plugin needs to be made
“Realtime”, enter its ID on a single line in the realtime-plugins.txt file.
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When adding PVS plugins to the disabled plugin list, ensure that a return carriage is entered after entering in the
last line of the plugin to be disabled. Failure to return to the next line could result in a non-functional disabled
plugin list.
Example: 1234 [return]
If any of the referenced files do not exist, simply create them using the appropriate method for the operating system. The file
locations are in the following table for each operating system.
Operating System
File Path
Linux
/opt/pvs/var/pvs
Windows
C:\ProgramData\Tenable\PVS\pvs\
Mac OS X
/Library/PVS/var/pvs
Detecting Encrypted and Interactive Sessions
The PVS can be configured to detect both encrypted and interactive sessions. An encrypted session is a TCP or UDP session
that contains sufficiently random payloads. An interactive session uses timing and statistical profiling of the packets in a
session to determine if the session involves a human typing at a command line prompt.
In both cases, the PVS will identify these sessions for the given port and IP protocol. It will then list the detected interactive
or encrypted session as a vulnerability.
The PVS has a variety of plugins to recognize telnet, Secure Shell (SSH), Secure Socket Layer, and other protocols. In
combination with the detection of the interactive and encryption algorithms, it is likely that the PVS will log multiple forms of
identification for the detected sessions.
For example, with a SSH service running on a high port, it is likely that the PVS would not only recognize this as an encrypted
session, it would also recognize the version of SSH and determine if there were any vulnerabilities associated with it.
Routes and Hop Distance
For active scans, one host can find the default route and an actual list of all routers between it and a target platform. To do
this, it sends one packet after another with a slightly larger TTL (time to live) value. Each time a router receives a packet, it
decrements the TTL value and sends it on. If a router receives a packet with a TTL value of one, it sends a message back to the
originating server that the TTL has expired. The server simply sends packets to the target host with greater and greater TTL
values, and collects the IP addresses of the routers in-between when they send their expiration messages.
Since the PVS is entirely passive, it cannot send or elicit packets from the routers or target computers. It can however, record
the TTL value of a target machine. The TTL value is an 8-bit field, meaning it can contain a value between 0 and 255. Most
machines use an initial TTL value of 32, 64, 128, or 255. Since there is a maximum of 16 hops between your host and any
other host on the internet, it is a simple algorithm that the PVS uses to map any TTL to the number of hops.
For example, if the PVS sniffed a server sending a packet with a TTL of 126, this is closest to 128 and two hops away. The PVS
does not know the IP address of the in-between routers.
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Modern networks have many devices such as NAT firewalls, proxies, load balancers, intrusion prevention,
routers, and VPNs that will rewrite or reset the TTL value. In these cases, the PVS can report some very odd hop
counts.
Alerting
When the PVS detects a realtime event, it can send the event to a local log file or send it via Syslog to a log aggregator such as
Tenable’s Log Correlation Engine as well as internal log aggregation servers and third party security event management
vendors.
New Host Alerting
The PVS can be configured to detect when a new host has been added to the network. This is not as simple as it sounds, and
several parameters can be configured within the PVS to increase or decrease the accuracy of detecting true change.
Initially, the PVS has no knowledge of your network’s active hosts. The first packets that the PVS sniffs would send an alert.
To avoid this, the PVS can be configured to learn the network over a period of days. Once this period is over, any “new” traffic
would be from a host that has not communicated during the initial training.
To prevent the PVS from having to relearn the network each time it starts, a file can be specified to save the active host
information. This file contains a list of all the current active hosts for the PVS. The scanner also requires that an interval to
update this file be specified. Tenable recommends an update time of at least one day (1440 minutes).
When the PVS logs a new host, the Ethernet address is saved in the message. When the PVS is more than one hop
away from the sniffed traffic, the Ethernet address will be that of the local switch, not the actual host. If the scanner
is deployed in the same collision domain as the sniffed server, the Ethernet address will be accurate.
For DHCP networks, the PVS will detect a “new” host very often. Tenable recommends deploying this feature on
non-volatile networks such as demilitarized zone (DMZ). Users should also consider analyzing PVS “new” host
alerts with Tenable’s SecurityCenter, which can sort realtime PVS events by networks.
Internal Passive Vulnerability Scanner IDs
What is a Passive Vulnerability Scanner ID?
This section describes the PVS’s advanced signature language for each plugin. Each vulnerability and realtime check that the
PVS performs has a unique associated ID. Since Tenable manages the Nessus vulnerability scanner, we have added the IDs
used by the PVS into the overall Nessus architecture. PVS IDs start from #00000 and go through #10000. Nessus IDs start
from #10001 and extend upward.
Internal Passive Vulnerability Scanner IDs
Some of the PVS’s checks, such as detecting open ports, are built in. The following chart lists some of the more commonly
encountered internal checks and describes what they mean:
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PVS ID
Name
Description
00000
Detection of open port
The PVS has observed a SYN-ACK leave from a server.
00001
Passive OS Fingerprint
The PVS has observed enough traffic about a server to perform a guess of the
operating system.
00002
Client Side Port Usage
The PVS has observed browsing traffic from a host.
00003
Internal Client Trusted
Connections
The PVS has logged a unique network session of source IP, destination IP and
destination port.
00004
Internal Interactive
Sessions
The PVS has detected one or more interactive network sessions between two hosts
within your focus network.
00005
Outbound Interactive
Sessions
The PVS has detected one or more interactive network sessions originating from
within your focus network and destined for one or more addresses on the Internet.
00006
Inbound Interactive
Sessions
The PVS has detected one or more interactive network sessions originating from
one or more addresses on the Internet to this address within your focus network.
00007
Internal Encrypted
Session
The PVS has detected one or more encrypted network sessions between two hosts
within your focus network.
00008
Outbound Encrypted
Session
The PVS has detected one or more encrypted network sessions originating from
within your focus network and destined for one or more addresses on the Internet.
00009
Inbound Encrypted
Session
The PVS has detected one or more encrypted network sessions originating from
one or more addresses on the Internet to this address within your focus network.
00012
Host TTL Discovered
The PVS logs the number of hops away each host is located.
00015
Internal Server Trusted
Connections
The PVS has logged a unique network session of source IP, destination IP, and
destination port.
00017
Realtime Server
Connection
The PVS has detected that a connection was enabled to a Realtime Syslog Server
Working with Passive Vulnerability Scanner Plugins
Vulnerability and Passive Fingerprint Overview
The PVS has two sources of “plugin” information: the .prmx and .prm plugin libraries in the plugins directory.
Tenable distributes its passive vulnerability plugin database in an encrypted format. This file is known as
tenable_plugins.prmx and can be updated on a daily basis, if necessary. PVS plugins that are written by the customer or
third parties have the extension of .prm.
Tenable has also implemented passive fingerprinting technology based on the open-source SinFP tool. With permission
from the author, Tenable has also included the database of passive operating system fingerprints for the fingerprinting
technology in this distribution of the PVS.
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Downloading New Vulnerability Plugins
When PVS is registered as a stand-alone scanner using an Activation Code, plugins are updated automatically every 24 hours
after the service is started. To manually update the PVS plugins from the web interface, navigate to the Feed Settings tab on
the Configuration page. Next, click the “Update Plugins” button next to the Activation Code box. The plugins may be updated
from the command line using the command “pvs --update-plugins”. If SecurityCenter is being used to manage a PVS,
new plugins for the PVS will automatically be sent at scheduled intervals and the PVS Proxy will restart the PVS as needed.
Writing Custom Plugin Libraries
PVS customers can write their own passive plugin libraries. These plugins are added into the plugins directory in the PVS’s
installation directory. The plugin library must end with a .prm extension for the PVS to see it. The next section details how to
write PVS plugins.
Restarting the Passive Vulnerability Scanner
Once new passive plugins are available to the PVS, it must be stopped and started to recognize the newly available plugins.
Writing Passive Vulnerability Scanner Plugins
Plugin Keywords
There are several keywords available for writing passive vulnerability plugins for PVS. Some of these keywords are
mandatory and some are optional. The mandatory keywords are highlighted in blue.
Name
Description
bid
Tenable assigns SecurityFocus Bugtraq IDs (BID) to PVS plugins. This allows a user
reading a report generated by the PVS to link to more information available at
http://www.securityfocus.com/bid. Multiple Bugtraq entries can be entered on one line
separated by commas.
bmatch
This is the same as “match” but can look for any type of data. A bmatch must always have
an even number of alphanumeric characters.
clientissue
If a vulnerability is determined in a network client such as a web browser or an email tool,
a server “port” will be associated with the reported vulnerability.
cve
Tenable also assigns Common Vulnerability and Exposure (CVE) tags to each PVS plugin.
This allows a user reading a report generated by the PVS to link to more information
available at http://cve.mitre.org/. Multiple CVE entries can be entered on one line
separated by commas.
dependency
This is the opposite of “noplugin”. Instead of specifying another plugin that has failed,
this keyword specifies which plugin has to have succeeded. This keyword specifies a PVS
ID that should exist in order for the plugin to be evaluated. In addition, this plugin can take
the form of “dependency=ephemeral-server-port”, which means that the server
being evaluated must have an open port above port 1024.
description
This field describes on one line the nature of the detected vulnerability. This data is
printed out by the PVS when printing the vulnerability report. Macros are available that
allow for the printing of matched network traffic such as banner information and are
discussed in the examples below. For line breaks, the characters “\n” can be used to invoke
a new line.
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Exploitability:
canvas
core
cvsstemporal
metasploit
Displays exploitability factors for the selected vulnerability. For example, if the
vulnerability is exploitable via both Canvas and Core and has a unique CVSS temporal
score, the following tags might be displayed in the plugin output:
CANVAS : D2ExploitPack
CORE : true
CVSSTEMPORAL : CVSS2#E:F/RL:OF/RC:C
These keywords are displayed only in vulnerabilities detected by PVS 3.4
and greater.
dport
Same as “sport”, but for destination ports.
family
Each Tenable plugin for the PVS is included in a family. This designation allows Tenable to
group PVS plugins into easily managed sets that can be reported on individually.
hs_dport
Same as “hs_sport” except for destination ports.
hs_sport
Normally, when the PVS runs its plugins, they are either free ranging looking for matches
on any port, or fixed to specific ports with the “sport” or “dport” keywords. In very high
speed networks, many plugins have a fall-back port, known as a high-speed port, which
focuses the plugin only on one specific port. In high speed more, the performance of a PVS
plugin with an “hs_sport” keyword is exactly the same as if the plugin was written with
the “sport” keyword.
id
Each PVS plugin needs a unique rule ID. Tenable assigns these 16 bit numbers within the
overall Nessus range of valid entries. Current plugin IDs can be listed at Tenable’s website
for the PVS.
match
This keyword specifies a set of one or more simple ASCII patterns that must be present in
order for the more complex pattern analysis to take place. The “match” keyword gives the
PVS a lot of its performance and functionality. With this keyword, if it does not see a
simple pattern, the entire plugin will not match.
name
This is the name of the vulnerability the PVS has detected. Multiple PVS plugins can have
the same name, but this is not encouraged.
nid
To track compatibility with the Nessus vulnerability scanner, Tenable has attempted to
associate PVS vulnerability checks with relevant Nessus vulnerability checks. Multiple
Nessus IDs can be listed under one “nid” entry such as “nid=10222,10223”.
nooutput
For plugins that are written specifically to be used as part of a dependency with another
plugin, the “nooutput” keyword will cause the PVS to not report anything for any plugin
with this keyword enabled.
noplugin
This keyword will prevent a plugin from being evaluated if another plugin has already
matched. For example, it may make sense to write a plugin that looks for a specific
anonymous FTP vulnerability, but have it disabled if another plugin that checked for
anonymous FTP had already failed.
pbmatch
Same as “bmatch” except for binary data on the previous side of the reconstructed
network session.
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plugin_output
This keyword displays dynamic data for a given vulnerability or event. The dynamic data is
usually represented using %L or %P, and its value is obtained from the regular expressions
defined using regex, regexi, pregex, or pregexi.
pmatch
This keyword is the same as “match” but is applied against the previous packet on the
other side of the reconstructed network session.
pregex
Same as “regex” except the regular expression is applied to the previous side of the
reconstructed network session.
pregexi
Same as “pregex” except the pattern matching is case insensitive.
protocol_id
This keyword is used to specify the protocol number of the protocol causing the plugin to
fire.
regex
This keyword specifies a complex regular expression search rule that will be applied to the
network session.
regexi
Same as “regex” except the pattern matching is case insensitive.
risk
All PVS plugins need a risk setting. Risks are classified as LOW, MEDIUM, or HIGH. A
LOW risk is an informational vulnerability such as an active port or service. A MEDIUM
risk is something that may be exploitable or discloses information and a HIGH risk is
something that is easily exploitable.
seealso
If one or more URLs are available, this keyword can be used to display them. Multiple
URLs can be specified on one line with commas. Example entries for this could include
CERT advisories and vendor information web sites. Note: PVS 3.0.x will only display the
last seealso defined in the PRM. PVS 3.2 and later will display multiple seealso
directives.
solution
If a solution is available, it can be described here. The report section will highlight the
solution with different text.
sport
This setting applies the PVS plugin to just one port. For example, it may make sense to
write a SNMP plugin that just looks for activity on port 162. However, for detection of offport services like a web server running on port 8080, a “sport” field would not be used in
the plugin.
timed-dependency
With this keyword, the functionality of the “noplugin” and “dependency” keywords is
slightly modified such that the evaluation must have occurred within the last “n” seconds.
udp
All plugins are assumed to be based on the TCP protocol unless this keyword is specified.
In addition to tcp or udp, the following protocols are supported: sctp, icmp, igmp, ipip, egp, pup, idp, tp, rsvp, gre,
pim, esp, ah, mtp, encap, pim, comp, raw or other.
Plugin Libraries
When writing PVS plugins in a .prm library, spaces are allowed, as are comment fields that start with a number ( # ) sign.
Each plugin must be separated with the word “NEXT” on a single line.
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Simply creating a .prm file in the plugins directory will make it available for use. PVS must be restarted for the new plugins
to be used.
Basic Passive Vulnerability Scanner Example
This plugin illustrates the basic concepts of PVS plugin writing:
id=1001
nid=11414
hs_sport=143
name=IMAP Banner
description=An IMAP server is running on this port. Its banner is :\n %L
risk=NONE
match=OK
match=IMAP
match=server ready
regex=^.*OK.*IMAP.*server ready
In this example, the following fields are used:

id is a unique number assigned to this plugin

nid is the Nessus ID of the corresponding Nessus NASL script

hs_sport is the source port to key on if we have the high-speed mode enabled

name is the name of the plugin

description is a description of the problem or service

match is the set of match patterns we must find in the payload of the packet before we evaluate the regular
expression

regex is the regular expression to apply to the packet payload
Notice that the description contains the %L macro. If this plugin evaluates successfully then the string pattern in the payload
that matched the regular expression is stored in %L and is printed out at report time.
More Complex Passive Vulnerability Scanner Example
id=1004
nid=10382
cve=CVE-2000-0318
bid=1144
hs_sport=143
name=Atrium Mercur Mailserver
description=The remote imap server is Mercur Mailserver 3.20. There is a flaw in this
server (present up to version 3.20.02) which allow any authenticated user to
read any file on the system. This includes other users mailboxes, or any system
file. Warning : this flaw has not been actually checked but was deduced from
the server banner
solution=There was no solution ready when this vulnerability was written; Please
contact the vendor for updates that address this vulnerability.
risk=HIGH
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match=>* OK
match=MERCUR
match=IMAP4-Server
regex=^\* OK.*MERCUR IMAP4-Server.*v3\.20\..*$
Notice that the first match pattern makes use of the “>” symbol. The “>” symbol indicates that the subsequent string must be
at the beginning of the packet payload. Use of the “>” symbol is encouraged where possible as it is an inexpensive operation.
Case Insensitive Example
There is a tool called SmartDownLoader that uploads and downloads large files. Unfortunately, versions 0.1 through 1.3 use
the syntax “SmartDownloader”, versions 1.4 through 2.7 use “smartdownloader” and versions 2.8 through current uses the
syntax “SMARTdownloader”. Searching for the various combinations of this text with purely the regex command would
cause us to use a statement that looks like this:
regex=[sS][mM][aA][rR][tT][dD]own[lL]oader
However, with the regexi command, the search string is much less complex and less prone to creating an error:
regexi=smartdownloader
By using regexi, we can more quickly match on all three versions as well as future permutations of the string
“smartdownloader”. In a case such as this, regexi is the logical choice.
id=8800
dependency=1442
hs_sport=6789
name=SmartDownLoader Detection
description=The remote host is running SmartDownLoader, a tool for performing
rudimentary uploads and downloads of large binary files.
solution=Ensure that this application is in keeping with Corporate policies and
guidelines
risk=MEDIUM
family=PeerToPeer
match=ownloader
regexi=smartdownloader
A complete example PVS plugin using the regexi keyword is shown above. The use of the match keyword searching for the
string “ownloader” is not a typo. By searching for network sessions that have this string in them first, the PVS can avoid
invoking the expensive regexi search algorithm unless the “ownloader” pattern is present.
Passive Vulnerability Scanner Network Client Detection
id=1010
hs_dport=25
clientissue
name=Buffer overflow in multiple IMAP clients
description=The remote e-mail client is Mozilla 1.3 or 1.4a which is vulnerable to a
boundary condition error whereby a malicious IMAP server may be able to crash
or execute code on the client.
solution=Upgrade to either 1.3.1 or 1.4a
risk=HIGH
match=^From:
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match=^To:
match=^Date:
match=^User-Agent: Mozilla
match=!^Received:
regex=^User-Agent: Mozilla/.* \(.*rv:(1\.3|1\.4a)
Match patterns that begin with the “^” symbol mean that at least one line in the packet payload must begin with the following
pattern. Match patterns that begin with the “!” symbol indicate that the string must NOT match anything in the packet
payload. In this case, the “!” and “^” symbols are combined to indicate that we should not evaluate any packet whose payload
contains a line starting with the pattern “Received:”.
The “^” is more expensive to evaluate than the “>” symbol. So, while both match patterns “^<pattern>” and “><pattern>”
would find “<pattern>” at the beginning of a packet payload, the use of “>” is more desirable as it is less costly. Use “^” when
looking for the occurrence of a string at the beginning of a line, but not at the beginning of the packet payload. In the latter
case, use the “>” character instead.
The Passive Vulnerability Scanner can Match “Previous” Packets
The PVS allows matching on patterns in the current packet as well as patterns in the previous packet in the current session. This
plugin shows how we can make use of this feature to determine if a Unix password file is sent by a web server:
id=1001
name=Password file obtained by HTTP (GET)
family=Generic
sport=80
description=It seems that a Unix password file was sent by the remote web server when
the following request was made :\n%P\nWe saw : \n%L
pmatch=>GET /
pmatch=HTTP/1.
match=root
match=daemon
match=bin
regex=root:.*:0:0:.*:.*
Here we see match patterns for a root entry in a Unix password file. We also see pmatch patterns that would match against
a packet that makes an HTTP GET request to a web server. The match patterns apply the current packet in a session and the
pmatch patterns apply to the packet that was captured immediately before the current one in the current session. To
explain this visually, we are looking for occurrences of the following:
1) client
GET / HTTP/1.*
-------------------------> server:port 80
2) client
Contents of password file:
root:.*:0:0:.*:.*
<------------------------- server:port 80
Our match pattern would key on the contents in packet 2) and our pmatch pattern would key on packet 1) payload contents.
The Passive Vulnerability Scanner can Match Binary Data
The PVS also allows matching against binary patterns. Here is an example plugin that makes use of binary pattern matching
to detect the usage of the well-known community string “public” in SNMPv1 response packets (The “#” is used to denote a
comment.):
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###
# SNMPv1 response
#
# Matches on the following:
# 0x30
- ASN.1 header
# 0x02 0x01 0x00
- (integer) (byte length) (SNMP version - 1)
# 0x04 0x06 public - (string) (byte length) (community string - "public")
# 0xa2
- message type - RESPONSE
# 0x02 0x01 0x00
- (integer) (byte length) (error status - 0)
# 0x02 0x01 0x00
- (integer) (byte length) (error index - 0)
###
id=1001
udp
sport=161
name=SNMP public community string
description=The remote host is running an SNMPv1 server that uses a well-known
community string - public
bmatch=>0:30
bmatch=>2:020100
bmatch=>5:04067075626c6963a2
bmatch=020100020100
Binary match patterns take the following form:
bmatch=[<>[off]:]<hex>
Binary match starts at <off>’th offset of the packet or at the last <offset> of the packet, depending on the use of > (start) or <
(end). <hex> is a hex string we look for.
bmatch=<:ffffffff
This will match any packet whose last four bytes are set to 0xFFFFFFFF.
bmatch=>4:41414141
This will match any packet that contains the string “AAAA” (0x41414141 in hex) starting at its fourth byte.
bmatch=123456789ABCDEF5
This will match any packet that contains the hex string above.
Negative Matches
PVS plugins can also be negated. Here are two examples:
pmatch=!pattern
pbmatch=>0:!414141
In each of these cases, the plugin would not match if the patterns contained in these “not” statements were present. For
example, in the first pmatch statement, if the pattern “pattern” were present, then the plugin would not match. In the second
statement, the binary pattern of “AAA” (the letter “A” in ASCII hex is 0x41) would match only if it were not presenting the
first three characters.
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Time Dependent Plugins
The last plugin example shows some more advanced features of the PVS plugin language that allows a plugin to be time
dependent as well as make use of the evaluation of other plugins. The plugin shows how the PVS can detect an anonymous
FTP server. The NEXT keyword is used to separate plugins the plugin file.
id=1018
nooutput
hs_sport=21
name=Anonymous FTP (login: ftp)
pmatch=^USER ftp
match=^331
NEXT #----------------------------------------------------------id=1019
dependency=1018
timed-dependency=5
hs_sport=21
name=Anonymous FTP enabled
description=The remote FTP server has anonymous access enabled.
risk=LOW
pmatch=^PASS
match=^230
Since we are trying to detect an anonymous FTP server we are going to be looking for the following traffic pattern:
1) FTP client
USER ftp
-----------------------> FTP server
2) FTP client
331 Guest login ok, ...
<----------------------- FTP server
3) FTP client
PASS [email protected]
-----------------------> FTP server
4) FTP client
230 Logged in
<----------------------- FTP server
Here we cannot use a single plugin to detect this entire session. So, instead we use two plugins: the first plugin looks for
packets 1) and 2) and the second plugin looks for packets 3) and 4).
A review of the above plugin shows that plugin 1018 matches 1) and 2) in the session by keying on the patterns “USER ftp” and
the 331 return code. Plugin 1019 matches on 3) and 4) by keying on the patterns “PASS” and the 230 return code.
Notice that plugin 1019 has the following field: dependency=1018. This field indicates the plugin 1018 must first evaluate
successfully before plugin 1019 may be evaluated (i.e., that plugin 1019 depends on plugin 1018’s success before it can be
evaluated).
One more step is needed to complete the plugin for the anonymous FTP session. We need to ensure that both plugins are
actually evaluating the same FTP session. We can do this by attaching a time dependency to plugin 1019. The field timedependency=5 indicates that plugin 1018 must have evaluated successfully in the last five seconds for 1019 to be
evaluated. In this way we can ensure that both plugins are evaluating the same FTP session.
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Writing Passive Vulnerability Scanner Realtime Plugins
Realtime Plugin Model
PVS realtime plugins are exactly the same as PVS vulnerability plugins with two exceptions:

they can occur multiple times

their occurrence may not be recorded as a vulnerability
For example, an attacker may attempt to retrieve the source code for a Perl script from an Apache web server. If the PVS
observes this event, it would be logical to send a realtime alert. It would also be logical to mark that the Apache server is
potentially vulnerable to some sort of Perl script source code download. In other cases, it may be more logical to just log the
attempt as an event, but not a vulnerability. For example, a login failure over FTP is an event that may be worth logging, but
does not indicate a vulnerability.
As the realtime plugins are written, there are two keywords that indicate to the PVS that these are not a regular vulnerability
plugin. These are the “realtime” and “realtimeonly” keywords. All keywords will be covered more in-depth in the next
session, but the basic difference of the “realtime” and “realtimeonly” keywords is that “realtime” events go into the
vulnerability database and the “realtimeonly” events do not.
In the previous example, the FTP user login failure would be marked as a “realtimeonly” event because we would like
realtime alerting, but not a new entry into the vulnerability database.
Keywords
Name
Description
realtime
If a plugin has this keyword, then the PVS will generate a SYSLOG message or realtime
log file entry the first time this plugin matches. This prevents vulnerabilities that are
worm related from causing millions of events. For example, the plugins for the Sasser
worm only generate one event. Output from plugins with this keyword will show up in
the vulnerability report.
realtimeonly
If a plugin has this keyword, then the PVS will generate a SYSLOG message or realtime
log file entry each time the plugin evaluates successfully. These plugins never show up in
the report file.
track-session
This keyword will cause the contents of a session to be reported (via SYSLOG or the
realtime log file) a specified number of times after the plugin containing this keyword
was matched. This is an excellent way to discover what a hacker “did next” or possibly
what the contents of a retrieved file were realtime.
trigger-dependency
Normally if a plugin has multiple dependencies, then all of those dependencies must be
successful for the current plugin to evaluate. However, the “trigger-dependency”
keyword allows a plugin to be evaluated as long as at least one of its dependencies is
successful.
Example Failed Telnet Login Plugin
The easiest way to learn about PVS realtime plugins is to evaluate some of those included by Tenable. Below is a plugin that
detects a failed Telnet login to a FreeBSD server.
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79
# Look for failed logins into an FreeBSD telnet server
id=0400
hs_sport=23
dependency=1903
Realtimeonly
name=Failed login attempt
description=PVS detected a failed login attempt to a telnet server
risk=LOW
match=Login incorrect
This plugin has many of the same features as a vulnerability plugin. The ID of the plugin is 0400. The high-speed port is 23.
We need to be dependent on plugin 1903 (which detects a Telnet service). The “realtimeonly” keyword tells the PVS that
if it observes this pattern, that it should alert on the activity, but not record any vulnerability.
Under the SecurityCenter, events from the PVS are recorded alongside other IDS tools.
Example Finger User List Enumeration Plugin
The finger daemon is an older Internet protocol that allowed system users to query remote servers to get information about
a user on that box. There have been several security holes in this protocol that allowed an attacker to elicit user and system
information that could be useful to attackers.
id=0500
dependency=1277
hs_sport=79
track-session=10
realtimeonly
name=App Subversion - Successful finger query to multiple users
description=A response from a known finger daemon was observed which indicated that
the attacker was able to retrieve a list of three or more valid user names.
risk=HIGH
match=Directory:
match=Directory:
match=Directory:
With this plugin, we are only looking for these patterns on systems where a working finger daemon has been identified
(dependency #1277). In this plugin though, we see the use of the “track-session” keyword. If this plugin is launched with a
value of 10, the session data from the next 10 packets is tracked and logged in either the SYSLOG or realtime log file.
During a normal finger query, if only one valid user is queried, then only one home directory will be returned. However, many of
the exploits for finger involve querying for users such as “NULL”, “0”, or “..”. This causes vulnerable finger daemons to return a
listing of all users. In that case, this plugin would be activated because of the multiple “Directory:” matches.
Example Unix Password File Download Web Server Plugin
This plugin below looks for any download from a web server that does not look like HTML traffic, but does look like the
contents of a generic Unix password file.
id=0300
dependency=1442
hs_sport=80
track-session=10
realtimeonly
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name=Web Subversion - /etc/passwd file obtained
description=A file which looks like a Linux /etc/passwd file was downloaded from a web
server.
risk=HIGH
match=!<HTML>
match=!<html>
match=^root:x:0:0:root:/root:/bin/bash
match=^bin:x:1:1:bin:
match=^daemon:x:2:2:daemon:
The plugin is dependent on PVS ID 1442, which detects web servers. In the match statements, we are attempting to ignore
any traffic that contains valid HTML tags, but also has lines that start with common Unix password file entries.
Example Generic Buffer Overflow Detection on Windows Plugin
One of the PVS’s strongest intrusion detection features is its ability to recognize specific services, and then to look for traffic
occurring on those services that should never occur unless they have been compromised. Since the PVS can keep track of both
sides of a conversation and make decisions based on the content of each, it is ideal to look for Unix and Windows command
shells occurring in services that should not have those command shells in them. Here is an example plugin:
# look for Windows error when a user tries to
# switch to a drive that doesn't exist
id=0201
include=services.inc
trigger-dependency
track-session=10
realtimeonly
name=Successful shell attack detected - Failed cd command
description=The results of an unsuccessful attempt to change drives on a Windows
machine occurred in a TCP session normally used for a standard service. This
may indicate a successful compromise of this service has occurred.
risk=HIGH
pmatch=!>GET
pregexi=cd
match=!>550
match=^The system cannot find the
match=specified.
This plugin uses the “include” keyword that identifies a file that lists several dozen PVS IDs, which identify well known
services such as HTTP, DNS, and NTP. The plugin will not even get evaluated unless the target host is running one of those
services.
The keyword “trigger-dependency” is needed to ensure the plugin is evaluated even if there is only one match in the
services.inc file. Otherwise, the PVS would only evaluate this plugin if the target host was running all PVS IDs present in
the services.inc file. The “trigger-dependency” keyword basically says that at least one PVS ID specified by one or
more dependency or include rules must be present.
Finally, the logic of plugin detection is looking for the following type of response on a Windows system:
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In this case, a user has attempted to use the “cd” command to change directories within a file system and the attempt was
not allowed. This is a very common event that occurs once a remote hacker has compromised a Windows 2000 or Windows
2003 server with a buffer overflow. What the PVS plugin is looking for in this specific event is a network session that should
not be there.
Looking at the plugin logic, there are “pmatch” and “pregexi” statements that attempt to ensure that the session is not an
HTTP session, and that the previous side of the session contains the string “cd”.
One could argue that the “pregexi” statement could be expanded to include the trailing space after the “d”
character and also the first character.
The plugin then looks for the expected results of the failed “cd” command. The first match statement makes sure this pattern
is not part of the FTP protocol. It turns out that looking for “cd” in one side of a session and the error of attempting to change
to a directory in an FTP session would cause false positives for this plugin. Adding a rule to ignore if a line starts with “550”
avoids this. While writing and testing this plugin, Tenable considered having a different set of plugins just for FTP, but the
additional filter statement took care of any false positives we had been seeing. Finally, the last two match statements look for
the results of the failed change directory attempt. They are spread across two match statements and could have been
combined into one regular expression statement, but there was enough content in the basic message to have them split into
higher-speed matching.
Passive Vulnerability Scanner Corporate Policy Plugins
Most companies have an “Acceptable Use Policy” that defines appropriate use of the company’s IT facilities. Often, this
policy is abused to some extent since detecting abuse can be difficult.
The PVS can help in this regard through use of PVS Corporate Policy plugins. These plugins can be used to look for policy
violations and items such as credit card numbers, Social Security numbers, and other sensitive content in motion.
Tenable ships PVS with a large number of plugins that are frequently updated. The primary focus of these plugins is to
discover hosts, applications and their related client/server vulnerabilities. The list of built-in PVS checks is available at the
following location:
http://static.tenable.com/dev/tenable_plugins.pdf
Many of the available plugins already detect activities that would fall into the “Inappropriate Use” category in most
companies. Some of the activities that are detected through these plugins include (but are not limited to):

game server detection

botnet client and server detection

peer to peer file serving

IRC server/client
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
chat clients

tunneling software or applications like Tor, GoToMyPC and LogMeIn
Detecting Custom Activity Prohibited by Policy
The plugins provided with PVS are useful for detecting generally inappropriate activities, but there may be times when more
specific activities need to be detected. For example, a company may want to have an alert generated when email is sent to a
competitor’s mail service or if users are managing their Facebook accounts from the corporate network.
Tenable provides the ability for users to write their own custom plugins, as documented in the section “Writing Passive
Vulnerability Scanner Plugins”. These plugins are saved as “prm” files.
The following example shows how to create a custom plugin to detect users logging into their Facebook accounts. First, a
unique plugin ID is assigned, in this case “9000”. So, the first line of our plugin will be:
id=9000
Next, we will want to have a description of what the vulnerability detects:
description=The remote client was observed logging into a Facebook account. You should
ensure that such behavior is in alignment with corporate policies and guidelines. For
your information, the user account was logged as:\n %L
The “%L” will be the results of our regular expression statement that will be created later. Basically, we want to log the
source address of the offending computer as well as the user ID that was used to log in. Next, we create a distinct name for
our plugin.
name=POLICY - Facebook usage detection
Note that the name begins with the string “POLICY”. This will make all POLICY violations easily searchable from the
SecurityCenter interface.
You could also define a SecurityCenter dynamic asset list that contains only POLICY violators.
The next field defines a “family”. For this example, the application is a web browser, so the family ID is defined as follows:
family=Web Clients
Since this is a web browser, a dependency can be assigned that will tell PVS to only look at clients that have been observed
surfing the web:
dependency=1735
Further, since we are looking at client traffic, we will define:
clientissue
Next, we assign a risk rating for the observed behavior:
risk=MEDIUM
In the final section we create “match” and “regex” statements that PVS will look for passively. We want all of these
statements to be true before the client is flagged for inappropriate usage:
match=>POST /
The web request must begin with a POST verb. This will weed out all “GET” requests.
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83
match=^Host: *.facebook.com
The statement above ensures that they are posting a host with a domain of “*.facebook.com”.
Finally, we have a match and regex statement that detects the user’s login credentials:
match=email=
regex=email=.*%40[^&]+
Putting it all together, we have a single plugin as follows:
id=9000
family=Web Clients
clientissue
dependency=1735
name=Facebook_Usage
description=The remote client was observed logging into a Facebook account.
You should ensure that such behavior is in alignment with
Corporate Policies and guidelines. For your information, the user account
was logged as:
risk=MEDIUM
solution=Stay off of Facebook.
match=>POST /
match=^Host: *.facebook.com
match=email=
regex=email=.*%40[^&]+
This plugin could be named Facebook.prm and added into the /opt/pvs/var/pvs/plugins/ directory. If the
SecurityCenter is being used to manage one or more PVS systems, use the plugin upload dialog to add the new .prm file.
If you wish to create a policy file that includes multiple checks, use the reserved word “NEXT” within the policy file. For
example:
id=9000
…
rest of plugin
…
NEXT
id=9001
…
etc.
Detecting Confidential Data in Motion
Many organizations want to ensure that confidential data does not leave the network. PVS can aid in this by looking at binary
patterns within observed network traffic. If critical documents or data can be tagged with a binary string, such as an MD5
checksum, the PVS will have the ability to detect these files being passed outside the network. For example:
Create a document that has a binary string of:
0xde1d7f362734c4d71ecc93a23bb5dd4c and
0x747f029fbf8f7e0ade2a6198560c3278
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84
A PVS plugin could then be created to look for this pattern as follows:
id=9005
trigger-dependency
dependency=2004
dependency=2005
hs_dport=25
description=POLICY - Confidential data passed outside the
corporate network. The Confidential file don'tshare.doc was
just observed leaving the network via email.
name=Confidential file misuse
family=Generic
clientissue
risk=HIGH
bmatch=de1d7f362734c4d71ecc93a23bb5dd4c
bmatch=747f029fbf8f7e0ade2a6198560c3278
These binary codes were created by simply generating md5 hashes of the following strings:
"Copyright 2006 BigCorp, file: don'tshare.doc"
"file: don'tshare.doc"
The security compliance group maintains the list of mappings (confidential file to md5 hash). The md5 hash can be embedded
within the binary file and could then be tracked as it traversed the network.
Similar checks can be performed against ASCII strings to detect, for example, if confidential data was cut-and-pasted into an
email. Simply create text watermarks that appear benign to the casual observer and map to a specific file name. For example:
"Reference data at \\192.168.0.2\c$\shares\employmentfiles for HR data regarding Jane
Mcintyre" could be a string which maps to a file named Finances.xls.
A PVS plugin could look for the string as follows:
id=9006
trigger-dependency
dependency=2004
dependency=2005
hs_dport=25
description=POLICY - Confidential data passed outside the
corporate network. Data from the confidential file Finances.xls was just
observed leaving the network via email.
name=Confidential file misuse
family=Generic
clientissue
risk=HIGH
match=Reference data at
match=192.168.0.2\c$\shares\employmentfiles
match=for HR data regarding Jane Mcintyre
The two example plugins above (IDs 9005 and 9006) would detect files leaving the network via email. Most corporations
have a list of ports that are allowed outbound access. SMTP is typically one of these ports. Other ports may include FTP,
Messenger client ports (e.g., AIM, Yahoo and ICQ), or Peer2Peer (e.g., GNUTELLA and BitTorrent). Depending on your
specific network policy, you may wish to clone plugins 9005 and 9006 to detect these strings on other outbound protocols.
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Passive Vulnerability Scanner Operating System Fingerprints
Passive Operating System Fingerprinting
Tenable uses a hybrid approach to operating system fingerprinting. Primarily, plugins are used to detect and identify the OS
of a host. If this is not possible, PVS will use detected packets to identify the OS.
The PVS has the ability to identify the likely operating system of a host by looking at the packets it generates. Specific
combinations of TCP packet entries, such as the window size and initial time-to-live (TTL) values, allow the PVS to predict the
operating system generating the traffic.
These unique TCP values are present when a server makes or responds to a TCP request. All TCP traffic is initiated with a
“SYN” packet. If the server accepts the connection, it will send a response that is known as a “SYN-ACK” packet. If the server
cannot or will not communicate, it will send a reset (RST) packet. When a server sends a “SYN” packet, the PVS will apply the
list of operating system fingerprints and attempt to determine the type of the operating system.
Tenable Network Security has received permission to re-distribute the passive operating fingerprints from the author of
SinFP open source project, which is available at:
http://www.gomor.org/sinfp
For Further Information
Tenable regularly updates PVS’s plugins and these can be viewed online at:
http://static.tenable.com/dev/tenable_plugins.pdf
An RSS feed of the latest plugins is available here:
http://www.tenable.com/pvs.xml
A document describing Tenable Product Plugin Families is available on the Tenable website:
http://static.tenable.com/documentation/Tenable_Products_Plugin_Families.pdf
Tenable Network Security, Inc. may be contacted via email for PVS support at [email protected] or [email protected]
About Tenable Network Security
Tenable Network Security provides continuous network monitoring to identify vulnerabilities, reduce risk, and ensure
compliance. Our family of products includes SecurityCenter Continuous View™, which provides the most comprehensive and
integrated view of network health, and Nessus®, the global standard in detecting and assessing network data. Tenable is
relied upon by many of the world’s largest corporations, not-for-profit organizations and public sector agencies, including the
entire U.S. Department of Defense. For more information, visit tenable.com.
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Appendix 1: Working with SecurityCenter
Architecture
One mode PVS operates under is under the control of a SecurityCenter that provides it with passive vulnerability data and
retrieves scanned data. SecurityCenter has a variety of reporting, remediation, and notification mechanisms to efficiently
distribute vulnerability information across large enterprises. In addition, it can also control a distributed set of Nessus active
vulnerability scanners. By combining active and passive vulnerability scanning, SecurityCenter can be used to efficiently and
accurately manage security across large networks.
Managing Vulnerabilities
A screen capture of SecurityCenter displaying a summary of vulnerabilities detected by the PVS is shown below. These
vulnerabilities can be independently viewed by many different users with different access control. SecurityCenter also
enables security managers to issue recommendations that help guide network administrators as to which vulnerabilities
should be mitigated.
Updating the PVS Management Interface
On occasion, the PVS management interface needs to be updated to provide new or updated features. When managed by
SecurityCenter 4.8.1 or earlier, the PVS web server and interface are not updated automatically by the plugins provided
through SecurityCenter. Therefore, when the web components are to be updated, it must be performed manually on each
PVS.
To manually update the plugins, first download the latest plugins using the URL created during the offline registration
process. Next, log in to the PVS interface as an admin user and navigate to the Configuration page, and then the Feed
Settings tab. The Offline Update section contains the “Browse” button, which opens a dialog box to allow you to select the
archive file to upload. Click the “Upload Archive” button to send the file to the PVS host, which will then update the plugins.
After stopping and starting the PVS service on the host, the new interface will be available for use.
The Passive Vulnerability Scanner is Realtime
Since the PVS’s vulnerability data is constantly being fed into SecurityCenter and PVS’s plugins are updated by Tenable, the
accuracy of the passive vulnerability data in SecurityCenter greatly enhances the quality of the security information
available to the SecurityCenter’s users.
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Appendix 2: Syslog Message Formats
PVS provides options to send realtime and vulnerability data as syslog messages. There are four formats of syslog files sent
from PVS as described here.
1. Syslog message format for syslog generated by realtime PRMs:
<priority>timestamp pvs:
src_ip:src_port|dst_ip:dst_port|protocol|plugin_id|plugin_name|matched_text_cur
rent_packet|matched_text_previous_packet|risk
2. Syslog message format for syslog generated by realtime PASL or vuln PRM or PASL:
<priority>timestamp pvs:
src_ip:src_port|dst_ip:dst_port|protocol|plugin_id|plugin_name|plugin_descripti
on|risk
3. Syslog message format for Open Port alert, Service Connection alert, Client and Server Connection alerts, Tracked
Sessions alert, New Host alert, and Accepts External Connection alert:
<priority>timestamp pvs:
src_ip:src_port|dst_ip:dst_port|protocol|plugin_id|plugin_name|plugin_specific_d
ata|risk
4. Encrypted/Interactive session alert:
<priority>timestamp pvs:
src_ip:src_port|dst_ip:dst_port|protocol|plugin_id|plugin_name|risk
The following table describes each field.
Name
Description
priority
The syslog facility level of the message.
timestamp
This field provides the date and time of the syslog message.
src_ip
This field is the source IP address reported for the traffic.
src_port
This field is the source port for the reported traffic.
dst_ip
This field is the destination IP address for the reported traffic.
dst_port
This field is the destination port for the reported traffic.
protocol
This reports the protocol used for the reported traffic.
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88
plugin_id
The reported PVS plugin id triggered by the reported traffic.
Some examples:
0 for open port alert
2 for service connection alert
3 for client connection alert
4 for internal interactive session
5 for outbound interactive session
6 for inbound interactive session
7 for internal encrypted session
8 for outbound encrypted session
9 for inbound encrypted session
10 for tracked sessions
13 for new host alert
14 for accepts external connection alert
15 for server connection alert
plugin_name
The name of the PVS plugin triggered by the reported traffic
Some examples:
'new-open-port' for open port alert
'connection-to-service' for service connection alert
'connection' for client connection alert
'tracked-session' for tracked session alert
'new-host-alert' for new host alert
'accepts-external-connections' for accepts external connection alert
'server-connection' for server connection alert
risk
The associated risk level of the reported vulnerability. This can be “NONE”, “LOW”,
“MEDIUM”, “HIGH”, or “INFO”.
matched_text_current_p
acket
Reports the payload which causes a match in the packet to trigger the PVS event.
matched_text_current_p
acket
Reports the payload from the other side of the session, which causes a match in the
packet to trigger the PVS event.
plugin_specific_data
The data provided is determined by the type of data reported.
Some examples:
‘new host alert’ is the value is the MAC address of the host
‘tracked session alert’ is the value of the payload of packet
This field is not applicable for “service connection” alert, “client connection” alerts,
“server connection” alerts, “open port alert”, and “accepts external connection” alert.
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Appendix 3: PVS Activation without Internet Access
If your PVS installation cannot reach the Internet directly, use the following procedure to register and update plugins:
On the system running PVS, type the following command:
Platform
Command to Run
Red Hat Linux /
CentOS
# /opt/pvs/bin/pvs –-challenge
Mac OS X
# /Library/PVS/bin/pvs --challenge
Windows
C:\Program Files\Tenable\PVS>pvs --challenge
This will produce a string called “challenge” that appears similar to following:
569ccd9ac72ab3a62a3115a945ef8e710c0d73b8
Next, go to https://plugins.nessus.org/offline-pvs.php and paste the “challenge” string as well as the Activation Code that you
received previously into the appropriate text boxes. This will produce a URL that will give you direct access to the PVS
plugins. Save this URL, which will be used every time you update your plugins. In addition, a file called nessus-fetch.rc
will be produced. Copy this file to the host running PVS in the appropriate directory:
Platform
Directory
Red Hat Linux /
CentOS
# /opt/pvs/etc/pvs/
Mac OS X
# /Library/PVS/etc/
Windows
C:\Program Files\Tenable\PVS\
Once the nessus-fetch.rc file has been copied, run the pvs –register-offline command to install the file:
Platform
Directory
Red Hat Linux /
CentOS
# /opt/pvs/bin/pvs --register-offline /opt/pvs/etc/pvs/nessus-fetch.rc
Mac OS X
# /Library/PVS/bin/pvs --register-offline /Library/PVS/etc/nessusfetch.rc
Windows
C:\Program Files\Tenable\PVS>pvs --register-offline "C:\Program
Files\Tenable\PVS\nessus-fetch.rc"
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The newest plugins can be obtained by going to the URL that was provided in the previous step. Here, you will receive a TAR
file (e.g., sc-passive.tar.gz). Copy the file to the PVS system and then type the appropriate command for your platform:
Platform
Command
Red Hat Linux /
CentOS
# /opt/pvs/bin/pvs --update-plugins /path/to/sc-passive.tar.gz
Mac OS X
# /Library/PVS/bin/pvs --update-plugins /path/to/sc-passive.tar.gz
Windows
C:\Program Files\Tenable\PVS>pvs --update-plugins C:\path\to\scpassive.tar.gz
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