Assessing the Y, and How, of the XZ Utils incident
High-end APT groups perform highly interesting social engineering campaigns in order to penetrate well-protected targets. For example, carefully constructed forum responses on precision targeted accounts and follow-up “out-of-band” interactions regarding underground rail system simulator software helped deliver Green Lambert implants in the Middle East. And, in what seems to be a learned approach, the XZ Utils project penetration was likely a patient, multi-year approach, both planned in advance but somewhat clumsily executed.
This recently exposed offensive effort slowly introduced a small cast of remote characters, communications, and malicious code to the more than decade old open-source project XZ Utils and its maintainer, Lasse Collin. The backdoor code was inserted in February and March 2024, mostly by Jia Cheong Tan, likely a fictitious identity. The end goal was to covertly implement an exclusive use backdoor in sshd by targeting the XZ Utils build process, and push the backdoored code to the major Linux distributions as a part of a large-scale supply chain attack.
While this highly targeted and interactive social engineering approach might not be completely novel, it is extraordinary. Also extraordinary is the stunningly subtle insertion of malicious code leveraging the build process in plain sight. This build process focus during a major supply chain attack is comparable only to the CozyDuke/DarkHalo/APT29/NOBELIUM Solarwinds compromise and the SUNSPOT implant’s cunning and persistent presence – its monitoring capability for the execution of a Solarwinds build, and its malicious code insertion during any Solarwinds build execution. Only this time, it’s human involvement in the build process.
