Hackers Eavesdropped on Encrypted Jabber Traffic for Months
On October 20, 2023, the administrator of jabber.ru (also known as xmpp.ru) discovered a man-in-the-middle attack targeting the XMPP (Jabber) instant messaging protocol. The attack involved intercepting encrypted TLS connections on the jabber.ru servers, which are hosted by Hetzner and Linode in Germany, along with related VPS environments.
The attackers redirected traffic through a transit node that substituted the TLS certificate for XMPP connections using the STARTTLS extension. Unknown individuals created a separate SSL certificate and proxied connections to TCP port 5222. The attack was uncovered due to a mistake by the attackers, who failed to renew the fake TLS certificate. The jabber.ru administrator encountered an error related to the expired certificate when attempting to connect to the service.
The fraudulent TLS certificate was obtained on April 18, 2023, via the Let’s Encrypt service. This allowed the attackers to intercept traffic to jabber.ru and xmpp.ru. Initially, there were concerns that the project server itself had been compromised, but an audit found no evidence of a breach.
It was also discovered that the certificate substitution occurred not only within Hetzner’s network but also within Linode’s network. Traffic to port 5222 on both providers’ networks was routed through an additional host. This led to suspicions that the attack could have been organized by someone with access to the providers’ infrastructure.
The certificate substitution stopped after the investigation began and the providers’ support teams were contacted. The project team suspects that the attack may have been carried out with the knowledge of the hosting providers, possibly under the supervision of German police or intelligence agencies.
Recommendations for Users
- All jabber.ru users are advised to change their access passwords.
- Check OMEMO and PGP keys for possible tampering.
- Consider all communications between the affected dates as compromised.
The attacker could have accessed contact lists, unencrypted message histories stored on the server, and even altered messages in real time. Encrypted communications using OMEMO, OTR, or PGP are only secure if both parties have verified their encryption keys.