Nessus

Setting Up The NST System To Run Nessus

If you plan on running the free version of Nessus that comes with the NST distribution, then follow these steps to setup Nessus using the NST Web User Interface (WUI):

• From the NST WUI menu bar, select System then Users & Passwords then NST Password.
• On the NST Password page, scroll down to the General area under Clear Text Passwords.
• Change the General clear text password to something you will remember and then press the Set General Password button. You will need to remember this password if you want to run the Nessus GUI client later.
• From the NST WUI menu bar, select Security then Active Scanners then Nessus Management.
• Press the Setup Nessus button.
• After the Nessus set up completes, press the Exit button.
• Press the Start button to start the nessusd service.
• Press the Return button.
• At this point the Nessus server should be set up and ready for use.
• You can fill in a IP Address and press the Start Scan button to verify your setup is operational.

Reducing The Load Nessus Puts On The System

When Nessus scans systems, it can perform multiple tests on multiple hosts simultaneously. This can put a rather large load on your NST system. In addition to the large load on your system, if you are running from a Live CD on a system with too little RAM, its possible to run out of memory and lock your system.

You can reduce the load by adjusting the "max_hosts", "max_checks", and "be_nice" settings found in the "/etc/nessus/nessusd.conf" file. The following snip of the "/etc/nessus/nessusd.conf" file demonstrates values you might use to reduce the load:

# Maximum number of simultaneous hosts tested : 
max_hosts = 3

# Maximum number of simultaneous checks against each host tested : 
max_checks = 5

# Niceness. If set to 'yes', nessusd will renice itself to 10.
be_nice = yes

Determining The Password For The Nessus Client

If you use the Nessus client, you'll be required to enter a user name and password when you connect to the Nessus server. By default, you will need to enter root as the user ID and the value of NSTCTPASSWD found in /etc/nst.conf.

This password is not set by the nstpasswd script which is used to set many of the encrypted passwords found on they system. The Nessus client/server installation on the NST requires a "clear text" password so the Nessus scans can be run directly from the NST WUI.

The Nessus server uses the value of the NSTCTPASSWD variable found in /etc/nst.conf. If you don't want to edit the file by hand, you can use the grep and sed commands to examine and change the "clear text" password used by Nessus. All changes need to be done PRIOR to starting up Nessus server.

[root@probe root]# grep NSTCTPASSWD /etc/nst.conf
NSTCTPASSWD="shoth7pheigh"
[root@probe root]# sed -i -e 's/^NSTCTPASSWD=.*/NSTCTPASSWD="NEWPASSWORD"/' /etc/nst.conf
[root@probe root]# grep NSTCTPASSWD /etc/nst.conf
NSTCTPASSWD="NEWPASSWORD"
[root@probe root]#

Enabling Logging

We discovered that the Nessus daemon likes to create very large log and dump files under the /var/nessus/logs directory. Unfortunately, this can chew through a lot of RAM on a live boot of the NST and result in system lock ups. So, by default, we have disabled much of the Nessus logging capabilities in the template /etc/nessus/nessusd.conf configuration file.

If you are using a hard disk installation, you may want to adjust some of the logging related parameters in the /etc/nessus/nessusd.conf file. In particular, look for the logfile, log_whole_attack, log_plugins_name_at_load, and dumpfile parameters. The following shows a snippet from the /etc/nessus/nessusd.conf file as how these parameters are initially set on a NST system:

# Log file (or 'syslog') :                                                       
#logfile = /var/log/nessus/nessusd.messages                                      
logfile = /dev/null

# Shall we log every details of the attack ?                                     
log_whole_attack = no

# Log the name of the plugins that are loaded by the server ?                    
log_plugins_name_at_load = no

# Dump file for debugging output, use `-' for stdout                             
#dumpfile = /usr/local/var/nessus/logs/nessusd.dump                              
dumpfile = /dev/null

Running Nessus In A Virtual Machine

It is possible to run Nessus within the NST Virtual Machine. This has several advantages over a Live CD boot (permanent disk storage for one). However, you may notice a significant performance hit when running Nessus from within a virtual machine.

Registering A Nessus Installation

Using The NST WUI

The NST WUI allows you to specify your Nessus activation code when updating the Nessus rules. The activation code only needs to be specified the first time you update your rules (leave the field blank on subsequent updates).

Using The Command Line

After setting up Nessus on a NST probe with the local rule set, you may decide that they would like to register your Nessus installation. This will greatly increase the number of rules Nessus will have at its disposal. In order to register your Nessus installation, you will need to request a registration code from the Nessus web site (http://www.nessus.org). You will then need to run the nessus-fetch command as shown below:

[root@nic /]# nessus-fetch --register 9732-2C31-316C-7C06-5A32
Your activation code has been registered properly - thank you.
Now fetching the newest plugin set from plugins.nessus.org...
Your Nessus installation is now up-to-date.
Make sure to call regularly use the command 'nessus-update-plugins' to stay up-to-date
To automate the update process, please visit <http://www.nessus.org/documentation/index.php?doc=cron>


[root@nic /]# 

Keeping The Nessus Rules Up To Date

After registering your system with Nessus, there are several ways to keep you Nessus plugins up to date.

• Use the NST WUI to update your Nessus plugins.
• Run the nessus-update-plugins command to manually update the plugins.
• Add a cron entry, or symbolic link to run the nessus-update-plugins command automatically (NOTE: the crond service must be running). The following would enable the updates once per day.

[root@nic ~] ln -s $(which nessus-update-plugins) /etc/cron.daily/
[root@nic ~] service crond start
Starting crond:                                            [  OK  ]
[root@nic ~] 

Upgrading To Nessus v4.2.2 (NST 2.13.0)

2010-Nov-11: This section describes the steps taken to install Nessus v4.2.2 onto a hard disk installation of NST v2.13.0. As software releases will change more quickly than this document, be aware that you may need to make adjustments.

Nessus offers enhanced versions of the Nessus Vulnerability Scanner software which we are not permitted to include in the NST distribution. However, you can download and install this enhanced version of the Nessus Vulnerability Scanner software yourself.

Caveats

There are some issues with upgrading to the full version of Nessus:

• You will not be able to use the NST WUI to manage your Nessus installation.
• The installation will require the removal of the nst-live and nst-additions packages.

Download Nessus

The first step to upgrading the Nessus software is to download the necessary package from the Nessus web site.

• Determine if your NST system is a 32 bit or 64 bit installation. Run the command below, if it reports i686 it indicates you have a 32 bit installation. If it reports x86_64 it indicates that you have a 32 bit installation.

[root@probe ~]# uname -m
i686
[root@probe ~]# 

• Go to the Nessus web site ([1]) and download the Linux package for Fedora 12/13. Pick the 32 bit version if you have a 32 bit NST installation. Pick the 64 bit version if you have a 64 bit NST installation.

Remove The Open Source Version of Nessus

Before installing the updated version of Nessus, you need to remove the Open Source version included with the NST distribution:

[root@cayenne ~]# yum remove nessus-core nessus-libraries

... Lot's of output as dependencies are checked ...

Dependencies Resolved

=================================================================================
 Package                 Arch    Version            Repository              Size
=================================================================================
Removing:
 nessus-core             i686    2.2.11-5.fc12      @released/$releasever  167 k
 nessus-libraries        i686    2.2.11-3.fc12      @released/$releasever  169 k
Removing for dependencies:
 libnasl                 i686    2.2.11-7.fc12      @released/$releasever  455 k
 libnasl-devel           i686    2.2.11-7.fc12      @fedora                3.2 k
 nessus-client           i686    2.2.11-5.fc12      @released/$releasever  228 k
 nessus-gui              i686    2.2.11-5.fc12      @released/$releasever  590 k
 nessus-libraries-devel  i686    2.2.11-3.fc12      @fedora                 89 k
 nessus-plugins-gpl      i686    2.2.11-3.nst13     @NstRepo/$releasever   4.0 M
 nessus-server           i686    2.2.11-5.fc12      @released/$releasever  515 k
 nst-additions           noarch  2.13.0-32.nst13    @NstRepo               0.0  
 nst-live                noarch  2.13.0-32.nst13    @NstRepo               0.0  

Transaction Summary
=================================================================================
Remove       11 Package(s)

Installed size: 6.1 M
Is this ok [y/N]: y

... More output as packages are removed ...

Complete!
[root@cayenne ~]# 

Install The Nessus RPM

After removing the Open Source version of Nessus that comes with the NST distribution, you can use the yum command to install the RPM file you downloaded from the Nessus web site. Using the yum command instead of the rpm command will enable the download and installation of any other package dependencies.

[root@cayenne ~]# yum --nogpgcheck localinstall /tmp/Nessus-4.2.2-fc12.i386.rpm 

... Dependency check output ...

=================================================================================
 Package      Arch       Version             Repository                     Size
=================================================================================
Installing:
 Nessus       i386       4.2.2-fc12          /Nessus-4.2.2-fc12.i386        11 M

Transaction Summary
=================================================================================
Install       1 Package(s)

Total size: 11 M
Installed size: 11 M
Is this ok [y/N]: y

... Installation output ...

Installed:
  Nessus.i386 0:4.2.2-fc12                                                       

Complete!
[root@cayenne ~]# 

Set Up

At this point you will need to configure and set up Nessus on your NST system. You can follow the standard Nessus Documentation to complete the installation. When reading the documentation remember to think of your NST system as being referenced as a Fedora 13 or Fedora Core 13 system in the Nessus documentation.