No antivirus detects this. Its the FBI Ransomware. I have seen this hundreds of times get passed Norton, Kaspersky, AVG, Avast, Avira and Bitdefender. That best thing to do is to download HitmanPro Kickstart then follow up with a MalwareBytes Antimalware scan. This infection usually happens when a user clicks on a random link without thinking. Essexboy can slso help you out. He is great at this stuff. But its not Avast’s fault. Safe surfing habits play a huge roll in this.

http://www.surfright.nl/en/kickstart

http://www.malwarebytes.org/

There are several versions of this. The code is changed daily so its impossible to keep up with it. Mac users are seeing this now. Here is great removal guide and or guides.

http://www.bleepingcomputer.com/virus-removal/