Trawling for Tor Hidden Services: Detection, Measurement, Deanonymization

Tor is the most popular volunteer-based anonymity network consisting of over 3000 volunteer-operated relays. Apart from making connections to servers hard to trace to their origin it can also provide receiver privacy for Internet services through a feature called "hidden services". In this paper we expose flaws both in the design and implementation of Tor\´s hidden services that allow an attacker to measure the popularity of arbitrary hidden services, take down hidden services and deanonymize hidden services. We give a practical evaluation of our techniques by studying: (1) a recent case of a botnet using Tor hidden services for command and control channels; (2) Silk Road, a hidden service used to sell drugs and other contraband; (3) the hidden service of the DuckDuckGo search engine.