Backtrack is a Linux distribution aimed at penetration testers, it
comes with a great collection of security tools and custom scripts
installed. Some of the tools are only usable by very advanced
users, other tools are so easy a kid can use them. I do have to
say, using most of these tools on systems you don't own yourself
and where you don't have permission by the owner, is likely to end
you without a job or in jail.
The latest release of backtrack, Backtrack 4 beta, is now based on
Ubuntu. In my opinion this is the best choice they could have made.
This makes it even easier for unexperienced users (read windows
system administrators) to use it. And in the process they learn to
use Linux, and they learn about the ease in which windows systems
are compromised. This makes them spread the word, show management
and promote Linux."