Tails is a live system that aims at preserving your privacy and anonymity. It helps you to use the Internet anonymously almost anywhere you go and on any computer but leave no trace using unless you ask it explicitly.

It is a complete operating-system designed to be used from a CD or a USB stick independently of the computer’s original operating system. It is Free Software and based on Debian GNU/Linux.
https://tails.boum.org/about/index.en.html