huntrule

Windows Rundll32 Execution Masquerading as Image Files via Image Extensions

Flags rundll32.exe executions whose command line references image file extensions used for DLL masquerading.

FreeReviewedSigma · High · v1
Product
windows
Category
process_creation
Author
Hieu Tran (SigmaHQ), DRL 1.1
Published
2023-03-13
Updated
2026-07-30
AnalysisDetection

ATT&CK techniques

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 identifies process creation events where rundll32.exe is executed while the command line includes common image file extensions (e.g., .png, .jpg, .gif). Attackers may use rundll32 to load DLL functionality while disguising the argument as an image to evade casual inspection and some content-based defenses. The detection relies on Windows process creation telemetry, matching the image path/end with rundll32.exe (and OriginalFileName) and the presence of specified image extensions in the command line.

Reporting behind it

Related detections9 linkedT1218.011 — drag to rearrange
Malicious Lunar Spider Loader Execution via rundll32 (via process_creation)
Malicious SYSTEM Persistence via Scheduled Task Running rundll32 at Startup (via process_creation)
Malicious Rundll32 Executing Image File as DLL
Suspicious Scheduled Task Executing Rundll32 DLL Export by Ordinal
Malicious Renamed Rundll32 Copied to Temp via Xcopy
Suspicious rundll32 Executing DLL from ProgramData (via process_creation)
Suspicious Rundll32 Loading DLL From Public or ProgramData Path via Process Creation (via process_creation)
Malicious LSASS Credential Dump via Rundll32 Comsvcs MiniDump via Process Creation (via process_creation)
Suspicious Rundll32 Execution Without a DLL Reference via Process Creation (via process_creation)
Windows Rundll32 Execution Masquerading as Image Files via Image Extensions
Pivot detection · T1218.011 · 9 related

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