Swati KhandelwalJun 12, 2026Linux / Network Security
Instead of hiding on the laptops and servers defenders watch most closely, a China-nexus group spent close to a decade hidden inside the Linux login system itself.
Sygnia, which tracks the group as Velvet Ant, says it backdoored the PAM and OpenSSH components that decide who is allowed to sign in, planting its access where ordinary cleanup could not reach it. The network it targeted had no direct internet access, so the group first staged through internet-facing systems to get there.
The earliest traces go back to 2016. Instead of dropping new malware that a scanner might catch, the attacker changed the trusted login programs themselves. Nothing obvious appeared, and no exploit was needed, so the activity looked like normal administration.
On many machines, the attacker replaced the main PAM login module with backdoored copies. Some let them in with a secret password; others quietly recorded real usernames and passwords as people logged in.
