The FBI warns of Internet-borne malware masquerading as a message from the law enforcement agency that locks computers until the user pays a fine for allegedly downloading and/or distributing illegal content. The malicious code is the Reveton virus, used in conjunction with the Citadel malware platform, that first came to the FBI s attention in 2011. The malware installs and immediately locks down the machine while replacing the monitor screen with a fake FBI warning that the user’s IP address has been linked to child pornography sites or other illegal online activity.
Source: https://threatpost.com/reveton-ransomware-uses-fake-fbi-message-extort-money-080912/76898/