BackTrack 5 is a “Penetration Testing Distribution”; it’s a specific linux distribution packed with all tools a security expert might need. These tools are used for system penetration or hacking (in the true sense of the word).
You can fetch a live CD, or usb-install.
I’ve always been an adept of the open source movement, and was an intensive Linux user during my university computer science studies.
I would like to quote:
“As a cryptography and computer security expert, I have never understood the current fuss about the open source software movement. In the cryptography world, we consider open source necessary for good security; we have for decades. Public security is always more secure than proprietary security. It’s true for cryptographic algorithms, security protocols, and security source code. For us, open source isn’t just a business model; it’s smart engineering practice.”