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Windows DLL Sideloading Indicator: JsSchHlp Loads JSESPR.dll from Untrusted Path

Alerts on unexpected loads of \JSESPR.dll, indicating possible DLL sideloading outside the Justsystem JsSchHlp directory.

FreeReviewedSigma · Medium · v2
Product
windows
Category
image_load
Author
frack113 (SigmaHQ), DRL 1.1
Published
2022-12-14
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 cases where a process loads the DLL named JSESPR.dll, but the DLL load path is not the expected JsSchHlp directory under Program Files\Common Files\Justsystem. Attackers may use DLL sideloading to execute malicious code under the guise of a legitimate application component. The detection relies on Windows image load telemetry that provides the loaded DLL filename and full load path.

Reporting behind it

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Suspicious wmicodegen.dll Sideload by inetinfo.exe (UAT-8099 Cobalt Strike)
Suspicious LucidRook DismCore.dll Side-Load into Browser Process
Suspicious Encrypted Implant File Creation for DLL Search Order Hijacking (RainyDay Turian PlugX)
Suspicious RoboForm Signed Binary Executed From Non-Standard Path (via process_creation)
Malicious dal_keepalives.dll Sideloaded By Signed Binary (via image_load)
Suspicious Cortex XDR Binary Sideloading winutils.dll (via image_load)
Windows DLL Sideloading Indicator: JsSchHlp Loads JSESPR.dll from Untrusted 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.