Since at least 2017, a mysterious threat actor has run thousands of malicious servers in entry, middle, and exit positions of the Tor network in what a security researcher has described as an attempt to deanonymize Tor users. The Record reports: Tracked as KAX17, the threat actor ran at its peak more than 900 malicious servers part of the Tor network, which typically tends to hover around a daily total of up to 9,000-10,000. Some of these servers work as entry points (guards), others as middle relays, and others as exit points from the Tor network. Their role is to encrypt and anonymize user traffic as it enters and leaves the Tor network, creating a giant mesh of proxy servers that bounce connections between each other and provide the much-needed privacy that Tor users come for. Servers added to the Tor network typically must have contact information included in their setup, such as an email address, so Tor network administrators and law enforcement can contact server operators in the case of a misconfiguration or file an abuse report. However, despite this rule, servers with no contact information are often added to the Tor network, which is not strictly policed, mainly to ensure there's always a sufficiently large number of nodes to bounce and hide user traffic.
But a security researcher and Tor node operator going by Nusenu told The Record this week that it observed a pattern in some of these Tor relays with no contact information, which he first noticed in 2019 and has eventually traced back as far as 2017. Grouping these servers under the KAX17 umbrella, Nusenu says this threat actor has constantly added servers with no contact details to the Tor network in industrial quantities, operating servers in the realm of hundreds at any given point. The actor's servers are typically located in data centers spread all over the world and are typically configured as entry and middle points primarily, although KAX17 also operates a small number of exit points. Nusenu said this is strange as most threat actors operating malicious Tor relays tend to focus on running exit points, which allows them to modify the user's traffic.
KAX17's focus on Tor entry and middle relays led Nusenu to believe that the group, which he described as "non-amateur level and persistent," is trying to collect information on users connecting to the Tor network and attempting to map their routes inside it. In research published this week and shared with The Record, Nusenu said that at one point, there was a 16% chance that a Tor user would connect to the Tor network through one of KAX17's servers, a 35% chance they would pass through one of its middle relays, and up to 5% chance to exit through one. While all signs point to a nation-level and well-resourced threat actor who is behind this group, neither Nusenu nor the Tor Project wanted to speculate.
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