User Shell Folders Registry Modification via CommandLine — Sigma Rule

Rule metadata and linked tags

Author: Swachchhanda Shrawan Poudel (Nextron Systems). Source status: experimental; severity: high. Source dates: 2026-01-05 / not supplied.

{
  "category": "process_creation",
  "product": "windows"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: fadd6a4a171e8a6e858a7853a6028f6ebb0b634777931287baaafaf3669bbfa0

Detection logic

Original source YAML. Source-tag agreement is not proof of complete semantic coverage. This rule has not been compiled for a SIEM backend or validated against live telemetry here.

title: User Shell Folders Registry Modification via CommandLine
id: 8f3ab69a-aa22-4943-aa58-e0a52fdf6818
related:
    - id: 9c226817-8dc9-46c2-a58d-66655aafd7dc
      type: similar
status: experimental
description: |
    Detects modifications to User Shell Folders registry values via reg.exe or PowerShell, which could indicate persistence attempts.
    Attackers may modify User Shell Folders registry values to point to malicious executables or scripts that will be executed during startup.
    This technique is often used to maintain persistence on a compromised system by ensuring that malicious payloads are executed automatically.
references:
    - https://www.welivesecurity.com/en/eset-research/muddywater-snakes-riverbank/
author: Swachchhanda Shrawan Poudel (Nextron Systems)
date: 2026-01-05
tags:
    - attack.persistence
    - attack.privilege-escalation
    - attack.defense-impairment
    - attack.t1547.001
    - attack.t1112
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - Image|endswith:
              - '\powershell.exe'
              - '\pwsh.exe'
              - '\reg.exe'
        - OriginalFileName:
              - 'powershell.exe'
              - 'pwsh.dll'
              - 'reg.exe'
    selection_cli_action:
        CommandLine|contains:
            - ' add ' # reg.exe modification
            - 'New-ItemProperty'
            - 'Set-ItemProperty'
            - 'si ' # short for Set-ItemProperty
    selection_cli_paths_root:
        CommandLine|contains:
            - '\Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders'
            - '\Software\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders'
    selection_cli_paths_suffix:
        CommandLine|contains: 'Startup' # covers both 'Startup' and 'Common Startup'
    condition: all of selection_*
falsepositives:
    - Usage of reg.exe or PowerShell to modify User Shell Folders for legitimate purposes; but rare.
level: high
regression_tests_path: regression_data/rules/windows/process_creation/proc_creation_win_user_shell_folders_registry_modification/info.yml
simulation:
    - type: atomic-red-team
      name: Change Startup Folder - HKLM Modify User Shell Folders Common Startup Value
      technique: T1547.001
      atomic_guid: acfef903-7662-447e-a391-9c91c2f00f7b

Original YAML and metadata in JSON

False positives

• Usage of reg.exe or PowerShell to modify User Shell Folders for legitimate purposes; but rare.

Source references

• https://www.welivesecurity.com/en/eset-research/muddywater-snakes-riverbank/