Discovering the XZ Backdoor with Andres Freund
Andres Freund, a PostgreSQL committer and performance expert, explains how he discovered the xz backdoor while benchmarking a performance patch. He detected anomalous CPU usage in sshd caused by injected code in liblzma, which was obfuscated to hide its malicious intent. The investigation revealed a sophisticated, likely state-sponsored attack that manipulated the build system and exploited dynamic linker features to intercept SSH authentication. Freund’s decision to rapidly disclose the vulnerability prevented widespread exploitation of Linux systems worldwide.