Windows Defender Context Menu Removed

Status: experimental
Severity: high
Log source: category process_creation, product windows
Author: Matt Anderson (Huntress)
Source: github.com/SigmaHQ/sigma

Detects the use of reg.exe or PowerShell to delete the Windows Defender context menu handler registry keys. This action removes the "Scan with Microsoft Defender" option from the right-click menu for files, directories, and drives. Attackers may use this technique to hinder manual, on-demand scans and reduce the visibility of the security product.

Known false positives

May be part of a system customization or "debloating" script, but this is highly unusual in a managed corporate environment.

MITRE ATT&CK coverage

Tactic	Techniques
Defense Impairment	`T1685` Disable or Modify Tools

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 1: Process creation

Rule body

title: Windows Defender Context Menu Removed
id: b9e8c7d6-a5f4-4e3d-8b1a-9f0c8d7e6a5b
related:
    - id: 72a0369a-2576-4aaf-bfc9-6bb24a574ac6
      type: similar
status: experimental
description: |
    Detects the use of reg.exe or PowerShell to delete the Windows Defender context menu handler registry keys.
    This action removes the "Scan with Microsoft Defender" option from the right-click menu for files, directories, and drives.
    Attackers may use this technique to hinder manual, on-demand scans and reduce the visibility of the security product.
references:
    - https://research.splunk.com/endpoint/395ed5fe-ad13-4366-9405-a228427bdd91/
    - https://winaero.com/how-to-delete-scan-with-windows-defender-from-context-menu-in-windows-10/
    - https://thedfirreport.com/2021/10/18/icedid-to-xinglocker-ransomware-in-24-hours/
    - https://blog.malwarebytes.com/malwarebytes-news/2021/02/lazyscripter-from-empire-to-double-rat/
author: 'Matt Anderson (Huntress)'
date: 2025-07-09
tags:
    - attack.defense-impairment
    - attack.t1685
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - Image|endswith:
              - '\powershell_ise.exe'
              - '\powershell.exe'
              - '\pwsh.exe'
              - '\reg.exe'
        - OriginalFileName:
              - 'powershell_ise.EXE'
              - 'PowerShell.EXE'
              - 'pwsh.dll'
              - 'reg.exe'
    selection_action:
        CommandLine|contains:
            - 'del'
            - 'Remove-Item'
            - 'ri '
    selection_reg_path:
        CommandLine|contains: '\shellex\ContextMenuHandlers\EPP'
    condition: all of selection_*
falsepositives:
    - May be part of a system customization or "debloating" script, but this is highly unusual in a managed corporate environment.
level: high

Stages and Predicates

Stage 0: `condition`

all of selection_*

Stage 1: `selection_img`

selection_img:
    - Image|endswith:
          - '\powershell_ise.exe'
          - '\powershell.exe'
          - '\pwsh.exe'
          - '\reg.exe'
    - OriginalFileName:
          - 'powershell_ise.EXE'
          - 'PowerShell.EXE'
          - 'pwsh.dll'
          - 'reg.exe'

Stage 2: `selection_action`

selection_action:
    CommandLine|contains:
        - 'del'
        - 'Remove-Item'
        - 'ri '

Stage 3: `selection_reg_path`

selection_reg_path:
    CommandLine|contains: '\shellex\ContextMenuHandlers\EPP'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`CommandLine`	match	`Remove-Item` corpus 2 (sigma 1, elastic 1) `\shellex\ContextMenuHandlers\EPP` `del` corpus 3 (sigma 2, splunk 1) `ri`	`field:"CommandLine" kind:match`
`Image`	ends_with	`\powershell.exe` corpus 179 (sigma 178, kusto 1) `\powershell_ise.exe` corpus 41 (sigma 41) `\pwsh.exe` corpus 165 (sigma 164, kusto 1) `\reg.exe` corpus 58 (sigma 58)	`field:"Image" kind:ends_with`
`OriginalFileName`	eq	`PowerShell.EXE` corpus 138 (sigma 84, splunk 30, elastic 24) `powershell_ise.EXE` corpus 51 (splunk 30, sigma 18, elastic 3) `pwsh.dll` corpus 112 (sigma 79, splunk 30, elastic 3) `reg.exe` corpus 43 (sigma 32, splunk 8, elastic 3)	`field:"OriginalFileName" kind:eq`