Security experts Alexander Volynkin and Michael McCord will present at the next Black Hat 2014 a method to break Tor network anonymity with just USD 3000. The two experts will show how to identify Tor users with a very small budget, just $3,000. According to the two experts a persistent adversary with a handful of powerful servers and a couple gigabit links can de-anonymize hundreds of thousands Tor clients and thousands of hidden services within a couple of months.”]
Source: https://securityaffairs.co/wordpress/26395/hacking/tor-network-broken.html