Nessus is a free, up to date and easy to use vulnerability scanner. You can find the official documentation of how to install Nessus here.

Download and install Nessus rpm package from the Nessus download page

[root@nessus chris]# rpm -ivh Nessus-3.0.6-es5.i386.rpm
Preparing… ########################################### [100%]
1:Nessus ########################################### [100%]
nessusd (Nessus) 3.0.6. for Linux
(C) 1998 – 2007 Tenable Network Security, Inc.
Processing the Nessus plugins…
[##################################################]
All plugins loaded
- Please run /opt/nessus//sbin/nessus-add-first-user to add an admin user
- Register your Nessus scanner at http://www.nessus.org/register/ to obtain
all the newest plugins
- You can start nessusd by typing /sbin/service nessusd start

[root@nessus chris]#

Add the first Nessus user, it will be the admin account

[root@nessus chris]# /opt/nessus/sbin/nessus-add-first-user
Using /var/tmp as a temporary file holder
Add a new nessusd user
———————-

Login : admin
Authentication (pass/cert) [pass] :
Login password :
Login password (again) :

User rules

———-

nessusd has a rules system which allows you to restrict the hosts
that admin has the right to test. For instance, you may want
him to be able to scan his own host only.
Please see the nessus-adduser(8) man page for the rules syntax
Enter the rules for this user, and hit ctrl-D once you are done :

(the user can have an empty rules set)

Login : admin
Password : ***********
DN :
Rules :
Is that ok ? (y/n) [y] y
user added.

Thank you. You can now start Nessus by typing :

/opt/nessus//sbin/nessusd -D

Start Nessus service daemon

[root@nessus chris]# /opt/nessus/sbin/nessusd -D &
[2] 1454
[root@nessus chris]# nessusd (Nessus) 3.0.6. for Linux
(C) 1998 – 2007 Tenable Network Security, Inc.

Processing the Nessus plugins…
[##################################################]
All plugins loaded
[2]- Done /opt/nessus/sbin/nessusd -D

[root@nessus chris]#

Obtain your Nessus registration code in the Nessus website and register your nessus installation.

[root@nessus chris]# /opt/nessus/bin/nessus-fetch –register putyourregcodehere
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.
If auto_update is set to ‘yes’ in nessusd.conf, Nessus will
update the plugins by itself.

[root@nessus chris]#

If you want a Windows-based Nessus admin console. Download and install Nessconnect