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Detection rules › Sigma

Outlook Security Settings Updated - Registry

Status
test
Severity
medium
Log source
product windows, category registry_set
Author
frack113
Source
github.com/SigmaHQ/sigma

Detects changes to the registry values related to outlook security settings

MITRE ATT&CK coverage

TacticTechniques
PersistenceT1137 Office Application Startup

Event coverage

ProviderEventTitle
SysmonEvent ID 13RegistryEvent (Value Set)

Rule body yaml

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

Stages and Predicates

Stage 0: condition

selection and not 1 of filter_main_*

Stage 1: selection

selection:
    TargetObject|contains|all:
        - '\SOFTWARE\Microsoft\Office\'
        - '\Outlook\Security\'

Stage 2: not filter_main_outlook

filter_main_outlook:
    Image|startswith:
        - 'C:\Program Files\Microsoft Office\'
        - 'C:\Program Files (x86)\Microsoft Office\'
    Image|endswith: '\OUTLOOK.EXE'

Exclusions

Top-level NOT(...) conjuncts: predicates this rule actively suppresses.

FieldKindExcluded values
Imagestarts_withC:\Program Files (x86)\Microsoft Office\
Imagestarts_withC:\Program Files\Microsoft Office\
Imageends_with\OUTLOOK.EXE

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

FieldKindValues
TargetObjectmatch
  • \Outlook\Security\
  • \SOFTWARE\Microsoft\Office\ corpus 4 (sigma 4)