Malicious MOVEit Transfer Web Shell X-siLock-Comment Header (via webserver)

ATT&CK techniques

Persistence → Exfiltration

Recon
Resource Dev
Initial Access
Execution
Persistence
- T1505.003Web Shell
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
- T1567Exfiltration Over Web Service
Impact

What it detects

This rule detects HTTP requests carrying the X-siLock-Comment header that the MOVEit Transfer web shell validates against a hardcoded value before executing operator commands. The header gates web shell actions driven by the instid header such as data retrieval and user deletion. Detecting this unique header is a high fidelity indicator of Cl0p web shell interaction.

Reporting behind it

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Malicious MOVEit Transfer Web Shell X-siLock-Comment Header (via webserver)

Pivot detection · T1505.003 · 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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