Tails (Debian based Linux distribution)  is a live operating system almost used on every computer enable to bootable from USB/Pendrive & DVD , first time release in June 23 2009 & used by edward snowden and completely encrypted.Tails is the world most secured operating system because all outgoing connections are forced to go through tor network & stop all unsecured connections and encrypt all your local files  .It allow you to use internet anonymously & circumvent censorships .Leave no trace on the computer on which  you using it.Tails is a open source project running by the financial support of The Tor Project. Easy to install & use, On 3 July 2014, German public television channel Das Erste reported that the NSA 's make a list of those people whose searching for tails or visiting tails website .In many countries using tor network is a crime so avoid using tails.