Suspicious Malicious IIS Module DLL Written to Inetsrv Directory (via file_event)

ATT&CK techniques

Persistence

Recon
Resource Dev
Initial Access
Execution
Persistence
- T1505.004IIS Components
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule detects the creation of a caches.dll file within the System32 inetsrv directory as used by the Larva-25003 IIS malware to host its native module. Dropping a new DLL into the inetsrv module directory is an unusual event outside of IIS feature installation.

Reporting behind it

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Windows IIS Configuration: New Module Added to /system.webServer/modules

Suspicious Malicious IIS Module DLL Written to Inetsrv Directory (via file_event)

Pivot detection · T1505.004 · 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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