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Windows Rcdll.dll DLL Sideloading via Image Load Path

Flags rcdll.dll loads from unexpected locations, excluding Visual Studio and Windows Kits directories.

FreeReviewedSigma · High · v2
Product
windows
Category
image_load
Author
X__Junior (Nextron Systems) (SigmaHQ), DRL 1.1
Published
2023-03-13
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 Windows processes that load rcdll.dll from any image path other than common Visual Studio and Windows Kits directories. Sideloading a DLL with a name like rcdll.dll can help an attacker execute unintended code while blending in with legitimate loading behavior. The detection relies on image load telemetry that records the loaded module path and matches those ending with rcdll.dll while excluding known software locations.

Reporting behind it

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Suspicious Loading of Masqueraded EndpointDlp.dll Backdoor
Suspicious Trend Micro Binary Sideloading tmdglog.dll
Suspicious DLL Sideloading via ProtonVPN Executable (via image_load)
Suspicious DLL Sideloading via OneDriveStandaloneUpdater (via image_load)
Windows Rcdll.dll DLL Sideloading via Image Load 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.