Suspicious File Immutability Set via chattr for Anti-Removal on Linux

ATT&CK techniques

Persistence → Defense Evasion

Recon
Resource Dev
Initial Access
Execution
Persistence
- T1543.002Systemd Service
Priv Esc
- T1543.002Systemd Service
Defense Evasion
- T1070.003Clear Command History
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule detects chattr setting the immutable attribute on a file, an anti-removal technique used by the PeerBlight Linux backdoor to protect its sshd-agent persistence from deletion. Making backdoor files immutable prevents defenders and admins from removing them without first clearing the attribute. Interactive chattr immutability changes on service files are uncommon and suspicious.

Reporting behind it

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Suspicious File Immutability Set via chattr for Anti-Removal on Linux

Pivot detection · T1543.002 · 9 related

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

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