“The operating system of all the official computers in Southern Naval Command (SNC) at Kochi is switching over to an exclusively designed Linux from Windows.
The uploading of new software is going at full swing. This is an after-effect of the shocking incident of leaking official naval secrets on the community sites.
The new OS will block all community sites and insecure web sites to the users of official computers. The new programme allows login internet but blocking uploading any documents through personal e-mails. There will be a strict official screening for all the internet activities of all employees.”
see Navy computers switching over to Linux OS
No doubt that other OS does provide facilities for tightening security but the extreme flexibility access to source code and the GPL provides allows them to get the job done better with GNU/Linux.
I recommend Debian GNU/Linux because of the ease of managing systems with the APT package management system.
A new version of Lightweight Portable Security (LPS), a Linux live CD with strong privacy protection features created by the United States Department of Defence, is out.
http://www.spi.dod.mil/lipose.htm