huntrule

Windows Registry: Detect windir Environment Key Changes for SilentCleanup UAC Bypass

Detects non-default Environment\windir registry changes commonly used to facilitate SilentCleanup UAC bypass.

FreeReviewedSigma · High · v1
Product
windows
Category
registry_set
Author
frack113, Nextron Systems (SigmaHQ), DRL 1.1
Published
2022-01-06
Updated
2026-07-30
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 flags registry set activity where the Environment\windir key is written to a non-default value. Attackers may modify windir to influence an auto-elevated cleanup task (SilentCleanup) that resides under %windir%\System32\cleanmgr.exe, enabling privilege escalation without UAC prompting. The detection relies on registry set telemetry targeting the Environment\windir path and excludes writes that match the default %SystemRoot% value.

Reporting behind it

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Windows Registry: Detect windir Environment Key Changes for SilentCleanup UAC Bypass
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.