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

Related detections9 linkedT1505.004 — drag to rearrange

Malicious Native IIS Module Loaded by w3wp Worker Process

Malicious BADIIS Native IIS Module Loaded by Worker Process (via image_load)

Malicious BadIIS C2 Communication via lwxatisme User-Agent

Suspicious BadIIS Native Module Registration via cmd Copy

Malicious Native IIS Module Installation via Appcmd by UAT-8099

Malicious BadIIS Module Load into IIS Worker Process by UAT-8099

Malicious Webserver IIS Configuration Edited - SYSMON (via file_event)

Malicious Webserver IIS Module Installed - Command (via process_creation)

Malicious Webserver IIS Module Installed - Command (via process_creation) - Variant 2

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.

Full detection rule

Unlock this rule to view and copy it

The detection logic is included with a plan. Everything else — context, mappings and implementation details — stays free on this page.

Sign in for 3 free unlocks

Signing in gives you 3 unlocks to spend on any rule in the library. No card, and they do not expire.

Also included

Unlocked rules convert on this page — to Splunk SPL or Splunk — Raw Index SPL or Microsoft Sentinel KQL or Microsoft Sentinel ASIM ASIM KQL or Microsoft Defender XDR KQL or Elastic Security KQL or Elastic Security Lucene or Elastic Security ES|QL or CrowdStrike Falcon CQL or SentinelOne PowerQuery or Palo Alto Cortex XDR XQL or Carbon Black Cloud Platform Search or Carbon Black EDR Process Search or Google Security Operations UDM Search or IBM QRadar AQL or Sumo Logic Cloud SIEM Rules expression or Rapid7 InsightIDR LEQL or Graylog Search or OpenSearch Lucene or OpenSearch PPL PPL or Grafana Loki LogQL or SQLite SQL or Zircolite SQLite — with the log-source profile the engine picked, the field map it used, and everything it could not express. Converting a rule you have unlocked costs no further credit.

See it run on a free rule →Convert your own rule →