huntrule

Malicious UAC Bypass via HKCU Environment windir Hijack

PremiumReviewedSigma · High · v1
Product
windows
Category
process_creation
Author
HuntRule
Published
2026-09-22
Updated
2026-09-22
AnalysisDetection

ATT&CK techniques

Priv Esc → 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 detects reg add writing a windir value under the HKCU Environment key, the environment-variable hijack half of the SilentCleanup UAC bypass used by NightshadeC2. The botnet set windir to its payload path so an auto-elevating scheduled task would launch its code with high integrity. Poisoning the windir user environment variable is a well-known privilege-escalation technique with no legitimate use.

Reporting behind it

Related detections9 linkedT1548.002 — drag to rearrange
Suspicious UAC Bypass via Fodhelper or Eventvwr Auto-Elevated Process
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Malicious UAC Bypass via Eventvwr Execution Hijack via Process Creation
Malicious UAC Bypass via Fodhelper or ComputerDefaults Execution Hijack via Process Creation
Malicious FodHelper UAC Bypass via ms-settings Shell Command Hijack (via registry_set)
Suspicious Banana RAT UAC Skip Environment Variable in PowerShell
Malicious UAC Bypass via sdclt Handler Hijack (via registry_set)
Malicious UAC Bypass via ms-settings Handler Hijack (via registry_set)
Malicious UAC Bypass via HKCU Environment windir Hijack
Pivot detection · T1548.002 · 9 related

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