Over 300 Tor Exit Nodes Hijacked to Intercept SSH Passwords and Deploy Ebury Backdoor

Attackers compromised hundreds of Tor exit nodes and repurposed them to perform man-in-the-middle attacks against SSH connections. Instead of reaching the intended server, users were redirected to attacker-controlled infrastructure where they could be tricked into accepting a forged host key and revealing their credentials. Researcher kaba identified 333 malicious exit nodes routing traffic through the same 12 interception servers after noticing an unexpected host-key warning on October 2. The campaign also attempted to install the Ebury Linux backdoor designed to steal authentication data. The Tor Project confirmed that operators' servers had their configurations altered and some middle relays were converted into exit nodes. The initial access vector remains unknown, but the activity window was limited to October 1-5. Users who connected via Tor during this period, accepted an unfamiliar key, and entered a password should treat their credentials as compromised.

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Attackers have turned more than 300 Tor exit nodes into infrastructure for intercepting SSH connections, redirecting users to malicious servers that could capture passwords.

Security researcher kaba examined roughly 3,000 exit nodes and found 333 that forwarded SSH traffic through the same set of 12 interception servers, representing approximately one in ten nodes by volume.

The anomaly was first noticed on 2 October when an SSH client displayed the familiar host-key mismatch warning. Accepting the forged key and entering credentials allowed the attackers to obtain access to the victim’s server.

In addition to credential theft, the campaign attempted to deploy Ebury, a Linux backdoor specifically built to harvest authentication data from compromised systems.

The Tor Project verified that the affected operators’ servers had been modified and that some intermediate relays had been converted into exit nodes. Compromised nodes are being removed from the network.

The initial compromise method used against the node operators is still unknown. The dangerous period lasted from 1 to 5 October, and the total number of victims remains undisclosed.

Anyone who established an SSH session through Tor during those dates, accepted an unfamiliar host key, and supplied a password should assume the credentials are compromised. Reliance on the anonymity network does not replace the need to verify the server identity before authentication.

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