Outlook Security Settings Updated - Registry

Hunt Hypothesis

Detects changes to the registry values related to outlook security settings

Detection Rule

Sigma (Original)

title: Outlook Security Settings Updated - Registry
id: c3cefdf4-6703-4e1c-bad8-bf422fc5015a
related:
    - id: 6763c6c8-bd01-4687-bc8d-4fa52cf8ba08 # EnableUnsafeClientMailRules
      type: similar
status: test
description: Detects changes to the registry values related to outlook security settings
references:
    - https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1137/T1137.md
    - https://learn.microsoft.com/en-us/outlook/troubleshoot/security/information-about-email-security-settings
author: frack113
date: 2021-12-28
modified: 2026-01-09
tags:
    - attack.persistence
    - attack.t1137
logsource:
    category: registry_set
    product: windows
detection:
    selection:
        TargetObject|contains|all:
            - '\SOFTWARE\Microsoft\Office\'
            - '\Outlook\Security\'
    filter_main_outlook:
        Image|startswith:
            - 'C:\Program Files\Microsoft Office\'
            - 'C:\Program Files (x86)\Microsoft Office\'
        Image|endswith: '\OUTLOOK.EXE'
    condition: selection and not 1 of filter_main_*
falsepositives:
    - Administrative activity
level: medium

KQL (Azure Sentinel)

imRegistry
| where (RegistryKey endswith "\\SOFTWARE\\Microsoft\\Office*" and RegistryKey endswith "\\Outlook\\Security*") and (not(((ActingProcessName startswith "C:\\Program Files\\Microsoft Office\\" or ActingProcessName startswith "C:\\Program Files (x86)\\Microsoft Office\\") and ActingProcessName endswith "\\OUTLOOK.EXE")))

Required Data Sources

False Positive Guidance

• Administrative activity

MITRE ATT&CK Context

• Tactic: Persistence
• Technique: T1137 — T1137

References

• https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1137/T1137.md
• https://learn.microsoft.com/en-us/outlook/troubleshoot/security/information-about-email-security-settings
• SigmaHQ Rule