Recording to report from famous IT technology website on March 17, 2014: belong to British Government Communications Headquarters (UK Government Communications Headquarters, GCHQ), responsible for assessing the security of electronic communications groups operating system and software security issues (Communications-Electronics Security Group, CESG), has released its latest research report - Ubuntu 12.04 is the safest operating system among many security operating system .
 

Report was aim at popular terminal operating system which used on desktop , smartphones and tablet computers including : Android 4.2 , Android devices Samsung 4.2, iOS 6, Blackberry 10.1, Google Chrome OS 26, Ubuntu 12.04, Windows 7 , and 8, Windows 8 RT and Windows Phone 8 and so on. Assessment process based on the British government security level classification (UK Government Security Classifications), the level is official level (OFFICIAL level, the lowest level of the British government security ) . Assessment indicates : Ubuntu 12.04 is the safest operating system.

More details：http://www.zdnet.com/uks-security-branch-says-ubuntu-most-secure-end-user-os-7000025312/