BackTrack Linux is the highest rated and acclaimed Linux security distribution to date. BackTrack is a Linux-based penetration testing arsenal that aids security professionals in the ability to perform assessments in a purely native environment dedicated to hacking.
BackTrack is intended for all audiences from the most savvy security professionals to early newcomers to the information security field. BackTrack promotes a quick and easy way to find and update the largest database of security tools collection to-date.
The community of users range from skilled penetration testers in the information security field, government entities, information technology, security enthusiasts, and individuals new to the security community.
Source: http://www.backtrack-linux.org/