Honey Onions: Exposing Snooping Tor HSDir Relays

Tor is a widely used anonymity network that protects users’ privacy and identity from corporations, agencies and governments. However, Tor remains a practical system with a variety of limitations which can be subverted. In particular, Tor’s security relies on the fact that a substantial number of its nodes do not misbehave. In this work we introduce, the concept of honey onions, a framework to detect misbehaving Tor relays with HSDir capability. This allows to obtain lower bounds on misbehavior among relays. We propose algorithms to both estimate the number of snooping HSDirs and identify the most likely snoopers. Our experimental results indicate that during the period of the study (72 days) at least 110 such nodes were snooping information about hidden services they host. We reveal that more than half of them were hosted on cloud infrastructure and delayed the use of the learned information to prevent easy traceback.