Tor Network Suffers IP Spoofing Attack Via Non-Exit Relays

In late October 2024, a coordinated IP spoofing attack targeted the Tor network, prompting abuse complaints and temporary disruptions.

While the attack affected non-exit relays and caused some relays to be taken offline, the overall impact on Tor users was limited.

Tor directory authorities, relay operators, and the Tor Project sysadmin team began receiving numerous abuse complaints alleging unauthorized port scanning activity.

The complaints were traced to a sophisticated IP spoofing attack. Attackers spoofed Tor-related IP addresses, particularly non-exit relays, to trigger automated abuse reports.

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The goal appeared to be the disruption of the Tor network by getting key IPs blacklisted by major hosting providers.

The attack caused significant inconvenience for relay operators, many of whom had to deal with their hosting providers blocking or suspending their relays due to the complaints.

Data centers like OVH and Hetzner were affected, with Tor relays falsely implicated in malicious activity. Despite this, the attack did not compromise the privacy or security of Tor users.

The origin of the spoofed IP packets was identified thanks to a collaborative effort involving the Tor community, InterSecLab, and GreyNoise.

The attack was brought under control on November 7, 2024. Key contributions came from security expert Andrew Morris and Pierre Bourdon, a relay operator who provided critical analysis of the nature of the attack.

If your hosting provider is still blocking access to the Tor network, the Tor Project has provided resources to resolve these issues.

Relay operators are advised to use OONI Probe’s “Circumvention” test to check directory authority reachability and share relevant information with their hosting providers to clarify the situation.

This incident underscored the strength and resilience of the Tor community. Relay operators worked together, troubleshooting issues and sharing knowledge to keep the network running smoothly.

The Tor Project expressed gratitude to all those involved and encouraged continued cooperation to protect the network from future threats.

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