Backtrack is a slackware based Linux distro which uses the KDE environment. Backtrack was developed by the Mati Aharoni, an Israeli security consultant.
This distro helps in extensive testings of workstations for security loopholes on both the system itself as well as on a network.
Today, from being a simple Slackware based distro, it is a complete security analysis tool used by professionals all over the world. Backtrack has taken computer security to such a level, that now we have a new field of education called “Offensive Security” with a certification, the education for which is focused around the use of this distro.
With a variety of spoofing tools, sniffers, tunneling softwares and much more, Backtrack is the perfect choice for any hacker or anyone interested in learning network exploits and ways to prevent them. It has more than 300 tools arranged categorically, and was awarded the #1 Security Live Distribution. It includes popular applications like Wireshark, chntpw etc. chntpw can be used to reset a lost password for windows. Other tools are also available for fun on computer networks.
Backtrack can be downloaded for free. The Version 3 is 700 MB in size, whereas the version 4 which is a pre-final version currently is 1.32 GB in size.
Get backtrack here.