FBI has been using a tactic called drive-by hacking to track computers using the Tor anonymous computing system. The FBI has owned up to these techniques in the past and tracked users across Tor before. Operation Torpedo is also used to track people legally visiting other suspicious sites like researchers or human rights workers. ACLU technologist Chris Soghoian worried that judges issuing the legal search warrants to the FBI which make these tracking malware attacks legal, don’t fully understand the technology. If you are also the one to use Tor to legally access potentially dangerous sites, no matter for what purpose you are there – THE FBI has an EYE on YOU.
Source: https://thehackernews.com/2014/08/warrant-authorized-fbi-to-track-and_16.html