mynetsecurity.blogspot.comNessus Vulnerability Scanner
Nessus is one of the best scanner hacking/security tool.Nessus is the world-leader in active scanners, featuring high speed discovery, configuration auditing, asset profiling, sensitive data discovery and vulnerability analysis of your security posture. Nessus scanners can be distributed throughout an entire enterprise, inside DMZs, and across physically separate networks.When Nessus is managed with Tenable's Security Center, an enterprise can perform full life-cycle vulnerability and configuration management. Organizations can communicate recommendations to the responsible parties, track remediations, and verify security patches and required configurations.
Some feature of Nessus:
1.Cost:Nessus is the best free network vulnerability scanner available, and the best to run on UNIX at any price. It is constantly updated, with more than 11,000 plugins for the free (but registration and EULA-acceptance required) feed.
2.Linux Platform:Key features include remote and local (authenticated) security checks, a client/server architecture with a GTK .
3.Graphical interface, and an embedded scripting language for writing your own plugins or understanding the existing ones. Nessus 3 is now closed source, but is still free-of-cost unless you want the very newest plugins.
How Nessus uses Nmap

Nessus is optimized to work with what we call "plugins". Plugins are implemented in such a way that it does not cost anything memory-wise to launch them -- the NASL interpreter is optimized in such a way that launching a plugin only uses several kilobytes. The operating system is not involved when a plugin is created, which makes the process execution fast and painless.However, since Nmap is an external application, Nessus calls it by launching a special plugin which actually executes the nmap binary, which is a costly operation. To make things worse, in the Nessus architecture each plugin is in charge of ONE host. This means that if you have configured Nessus to scan forty hosts at the time, then there will be forty instances of Nmap running in memory.If you are familiar with Nmap and want to use it for your scan, then run it from the command-line first, and save the results in 'greppable' output:

# nmap -n -sS -p1-65535 -oG nmap-results.txt

You can then import the results in Nessus directly (in the plugins preferences -> Nmap NASL Wrapper -> File containing Nmap results). This will prevent Nessus from re-scanning your network. You will need the nmap.nasl plugin.

To use Nmap from within Nessus:
Download and copy nmap.nasl to your plugins directory: # cp nmap.nasl /opt/nessus/lib/nessus/plugins/
Restart nessusd: # killall nessusd
# /opt/nessus/sbin/nessusd -D
Next time you connect to Nessus, your client should display a new port scanner (Nmap NASL Wrapper). If not, then it probably means that nmap is not in your $PATH when you are starting nessusd.

You can Download NESSUS By clicking here