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Windows: Detect Microsoft Office DLL sideloading via ImageLoad of outllib.dll from nonstandard path

Alerts on outllib.dll loads from non-standard locations rather than typical Microsoft Office directories.

FreeReviewedSigma · High · v2
Product
windows
Category
image_load
Author
Nasreddine Bencherchali (Nextron Systems), Wietze Beukema (project and research) (SigmaHQ), DRL 1.1
Published
2022-08-17
Updated
2026-07-31
AnalysisDetection

ATT&CK techniques

Execution → Defense Evasion

  1. Recon

  2. Resource Dev

  3. Initial Access

  4. Execution

  5. Persistence

  6. Priv Esc

  7. Defense Evasion

  8. Cred Access

  9. Discovery

  10. Lateral Movement

  11. Collection

  12. C2

  13. Exfiltration

  14. Impact

What it detects

This rule flags process DLL loads where the loaded module name ends with outllib.dll while the originating path is not one of the standard Microsoft Office installation directories. DLL sideloading can allow attackers to execute malicious code by forcing an application to load an attacker-controlled library. The detection relies on image-load telemetry that includes the loaded DLL path or filename (e.g., ImageLoaded) to distinguish nonstandard locations from expected Office directories.

Reporting behind it

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Windows: Detect Microsoft Office DLL sideloading via ImageLoad of outllib.dll from nonstandard path
Pivot detection · T1574.001 · 9 related

Changelog

v2
  1. v2
    Candidate ingested via manual entry.2026-07-31
  2. v1
    No changelog recorded for this version.2026-07-30

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