Researchers at Northeastern University were curious about how the Tor anonymity network handled hidden services nodes. They figured out a way to come up with a honeypot that targets those servers that have the hidden service flag, HSDir, set.

The node running a hidden service in Tor depends totally on the relay of nodes that serve it. They are supposed to be incorruptible. But as this recent research showed, that’s not always the case.

Honey Onions

According to the report, the researchers developed a framework called honey onions (HOnions) “to detect and identify misbehaving and snooping HSDirs.” The system identified at least 110 snooping relays during a 72-day period. More than half were hosted on cloud infrastructure, which made them hard to trace.

What if this is just some botnet activity? According to the report, most of the recorded visits were automated to query the root path of the server. The sheer number of hidden services, however, seems to rule out the botnet theory.

All Snoops Are Not Equal

So what are the snoopers doing? The researchers concluded that “not all snooping HSDirs operate with the same level of sophistication.” That’s an interesting observation.

Some malicious Tor nodes avoided the detection of daily HOnions but were later picked up by weekly and monthly HOnions, the report stated. Researchers further detailed the difficulty in detecting nodes hosted on cloud infrastructure. In fact, the authors seem to think that the cloud is a great platform for a Tor attack.

Securing the Tor Anonymity Network

After further analysis, researchers found Apache and search engine-related queries. They also documented attempts to find or exploit SQL injection, cross-site scripting (XSS), Drupal user enumeration, path traversal, Ruby on Rails and PHP vulnerabilities.

According to SecurityWeek, the majority of malicious relays are located in the U.S., Germany, France, U.K. and the Netherlands. There are more than 3,000 relays with the HSDir flag, according to the Tor Project.

In the future, the researchers hope to “propose algorithms to both estimate the number of snooping HSDirs and identify them.” Until more information is revealed, however, Tor users will have to think twice about their true level of privacy.

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