huntrule

Windows Registry: Outlook EnableUnsafeClientMailRules Set to 1

Alerts when Outlook’s EnableUnsafeClientMailRules registry value is enabled (DWORD 0x1), reducing mailbox macro/script protections.

FreeReviewedSigma · High · v1
Product
windows
Category
registry_set
Author
Nasreddine Bencherchali (Nextron Systems) (SigmaHQ), DRL 1.1
Published
2023-02-08
Updated
2026-07-30
AnalysisDetection

ATT&CK techniques

Persistence → 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 changes in the Windows registry where Outlook’s EnableUnsafeClientMailRules value is set to DWORD 0x00000001 under the Outlook\Security path. Enabling this setting reduces Outlook security controls, allowing client mail rules to start applications or execute macros. It relies on registry set telemetry that records the TargetObject ending with \Outlook\Security\EnableUnsafeClientMailRules and the written value.

Reporting behind it

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Suspicious Registry Value under Console WindowsUpdates for C2 Storage
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Windows Registry: Outlook EnableUnsafeClientMailRules Set to 1
Pivot detection · T1112 · 9 related

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