TorScan: Tracing Long-lived Connections and Differential Scanning Attacks

Tor is a widely used anonymity network providing low-latency communication capabilities. Around 400,000 users per day use Tor to route TCP traffic through a sequence of relays; three hops are selected from a pool of currently almost 3000 volunteer-operated Tor relays to comprise a route through the network for a limited time. In comparison to single-hop proxies, forwarding TCP streams through multiple relays increases the anonymity of the users significantly: each hop along the route only knows its successor and predecessor. The anonymity provided by Tor heavily relies on the hardness of linking a user's entry and exit nodes.