Windows Defender Exclusion Registry Key - Write Access Requested

Status: test
Severity: medium
Log source: product windows, service security
Author: @BarryShooshooga, Nasreddine Bencherchali (Nextron Systems)
Source: github.com/SigmaHQ/sigma

Detects write access requests to the Windows Defender exclusions registry keys. This could be an indication of an attacker trying to request a handle or access the object to write new exclusions in order to bypass security.

MITRE ATT&CK coverage

Tactic	Techniques
Defense Impairment	`T1685` Disable or Modify Tools

Telemetry coverage

Provider	Record / event type
Security-Auditing	Event ID 4656: A handle to an object was requested.
Security-Auditing	Event ID 4663: An attempt was made to access an object.

Rule body

title: Windows Defender Exclusion Registry Key - Write Access Requested
id: e9c8808f-4cfb-4ba9-97d4-e5f3beaa244d
related:
    - id: 46a68649-f218-4f86-aea1-16a759d81820
      type: derived
    - id: a33f8808-2812-4373-ae95-8cfb82134978
      type: derived
status: test
description: |
    Detects write access requests to the Windows Defender exclusions registry keys. This could be an indication of an attacker trying to request a handle or access the object to write new exclusions in order to bypass security.
references:
    - https://www.bleepingcomputer.com/news/security/gootkit-malware-bypasses-windows-defender-by-setting-path-exclusions/
author: '@BarryShooshooga, Nasreddine Bencherchali (Nextron Systems)'
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:
        AccessList|contains:
            - '%%4417' # WriteData
            - '%%4418' # AppendData
        EventID:
            - 4656 # A handle to an object was requested.
            - 4663 # An attempt was made to access an object.
        ObjectName|contains: '\Microsoft\Windows Defender\Exclusions\'
    condition: selection
falsepositives:
    - Unknown
level: medium

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

selection:
    AccessList|contains:
        - '%%4417'
        - '%%4418'
    EventID:
        - 4656
        - 4663
    ObjectName|contains: '\Microsoft\Windows Defender\Exclusions\'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`AccessList`	match	`%%4417` corpus 11 (sigma 8, elastic 2, splunk 1) `%%4418` corpus 3 (sigma 1, splunk 1, kusto 1)	`field:"AccessList" kind:match`
`ObjectName`	match	`\Microsoft\Windows Defender\Exclusions\` corpus 2 (sigma 2)	`field:"ObjectName" kind:match value:"\Microsoft\Windows Defender\Exclusions\"`