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Detection rules › Sigma

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

TacticTechniques
Defense ImpairmentT1685 Disable or Modify Tools

Event coverage

ProviderEventTitle
Security-AuditingEvent ID 4656A handle to an object was requested.
Security-AuditingEvent ID 4663An attempt was made to access an object.

Rule body yaml

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

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
AccessListmatch
  • %%4417 corpus 11 (sigma 8, elastic 2, splunk 1)
  • %%4418 corpus 3 (sigma 1, splunk 1, kusto 1)
ObjectNamematch
  • \Microsoft\Windows Defender\Exclusions\ corpus 2 (sigma 2)