Tor Anonymity Not 100 Percent Guaranteed

January 1, 2017

An article at Naked Security reveals some information turned up by innovative Tor-exploring hidden services in its article, “‘Honey Onions’ Probe the Dark Web: At Least 3% of Tor Nodes are Rogues.” By “rogues,” writer Paul Ducklin is referring to sites, run by criminals and law-enforcement alike, that are able to track users through Tor entry and/or exit nodes. The article nicely lays out how this small fraction of sites can capture IP addresses, so see the article for that explanation. As Ducklin notes, three percent is a small enough window that someone just wishing to avoid having their shopping research tracked may remain unconcerned, but is a bigger matter for, say, a journalist investigating events in a war-torn nation. He writes:

Two researchers from Northeastern University in Boston, Massachussets, recently tried to measure just how many rogue HSDir nodes there might be, out of the 3000 or more scattered around the world. Detecting that there are rogue nodes is fairly easy: publish a hidden service, tell no one about it except a minimum set of HSDir nodes, and wait for web requests to come in.[…]

With 1500 specially-created hidden services, amusingly called ‘Honey Onions,’ or just Honions, deployed over about two months, the researchers measured 40,000 requests that they assume came from one or more rogue nodes. (Only HSDir nodes ever knew the name of each Honion, so the researchers could assume that all connections must have been initiated by a rogue node.) Thanks to some clever mathematics about who knew what about which Honions at what time, they calculated that these rogue requests came from at least 110 different HSDir nodes in the Tor network.

It is worth noting that many of those requests were simple pings, but others were actively seeking vulnerabilities. So, if you are doing anything more sensitive than comparing furniture prices, you’ll have to decide whether you want to take that three percent risk. Ducklin concludes by recommending added security measures for anyone concerned.

Cynthia Murrell, January 1, 2017

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