Have you encountered the Reveton variant of Citadel Malware?
One of the employees here was freaking out when his computer locked and displayed a message that it had been identified as a visiting and viewing websites containing illegal content and had been locked by the Computer Crime and Intellectual Property Section of the US Department of Justice.
Read more: Have you encountered the Reveton variant of Citadel Malware?
Story added 2. May 2012, content source with full text you can find at link above.