It's a hoax. I don't know if it's detected as most of these things aren't activated unless someone clicks on them. That website must have been compromised, I suggest avoiding it in future..
There is a good removal guide for it here: http://www.bleepingcomputer.com/virus-removal/remove-mandiant-usa-cyber-security -ransomware
See the last link in my signature below for ideas regarding ransomware and some free tools that can be used.
None of the regular antivirus applications catch them because of the way they work.
It's a hoax.
Well, not exactly a hoax.
this is a computer infection and not a legitimate message from any government agency
See this Microsoft page for some more information.
I meant a scam, sorry.