Windows Defender Exclusion List Modified

Status: test
Severity: medium
Log source: product windows, service security
Author: @BarryShooshooga
Source: github.com/SigmaHQ/sigma

Detects modifications to the Windows Defender exclusion registry key. This could indicate a potentially suspicious or even malicious activity by an attacker trying to add a new exclusion in order to bypass security.

Known false positives

Intended exclusions by administrators

MITRE ATT&CK coverage

Tactic	Techniques
Defense Impairment	`T1685` Disable or Modify Tools

Telemetry coverage

Provider	Record / event type
Security-Auditing	Event ID 4657: A registry value was modified.

Rule body

title: Windows Defender Exclusion List Modified
id: 46a68649-f218-4f86-aea1-16a759d81820
related:
    - id: e9c8808f-4cfb-4ba9-97d4-e5f3beaa244d
      type: derived
    - id: a33f8808-2812-4373-ae95-8cfb82134978
      type: derived
status: test
description: |
    Detects modifications to the Windows Defender exclusion registry key. This could indicate a potentially suspicious or even malicious activity by an attacker trying to add a new exclusion in order to bypass security.
references:
    - https://www.bleepingcomputer.com/news/security/gootkit-malware-bypasses-windows-defender-by-setting-path-exclusions/
author: '@BarryShooshooga'
date: 2019-10-26
modified: 2023-11-11
tags:
    - attack.defense-impairment
    - attack.t1685
logsource:
    product: windows
    service: security
    definition: 'Requirements: Audit Policy : Security Settings/Local Policies/Audit Policy, Registry System Access Control (SACL): Auditing/User'
detection:
    selection:
        EventID: 4657 # A registry value was modified.
        ObjectName|contains: '\Microsoft\Windows Defender\Exclusions\'
    condition: selection
falsepositives:
    - Intended exclusions by administrators
level: medium

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

selection:
    EventID: 4657
    ObjectName|contains: '\Microsoft\Windows Defender\Exclusions\'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`ObjectName`	match	`\Microsoft\Windows Defender\Exclusions\` corpus 2 (sigma 2)	`field:"ObjectName" kind:match value:"\Microsoft\Windows Defender\Exclusions\"`