In April 2013, a piece of malware was found embedded in Freedom Hosting’s darknet server that would exploit a security hole in a particular web browser and execute code on the user’s computer. This code gathered some information about the user and sent it to a server in Virginia and then crashed – it had no obvious malicious intent that is so characteristic of malware. It was therefore theorised that the FBI, who have offices in Virginia, and who have ‘form’ for writing malware, may have authored it – this now appears to be true.
http://oweng.myweb.port.ac.uk/fbi-tor-malware-analysis/