huntrule

Windows Process Creation: reg.exe Modifying Group Policy Registry Settings

Flags reg.exe commands targeting Group Policy System registry settings related to security and policy refresh.

FreeUnreviewedSigmamediumv1
title: "Windows Process Creation: reg.exe Modifying Group Policy Registry Settings"
id: b4c32cf9-5bf0-4203-99ba-f04e27ffc224
related:
  - id: b7216a7d-687e-4c8d-82b1-3080b2ad961f
    type: similar
  - id: ada4b0c4-758b-46ac-9033-9004613a150d
    type: derived
status: test
description: This rule identifies Windows process executions where reg.exe is used to modify registry values under the Group Policy System policy path. Attackers can use GPO-related policy changes to enable or alter security-relevant behavior across endpoints without deploying new binaries. The detection relies on process creation telemetry (Image/OriginalFileName and CommandLine) and matches specific Group Policy setting names within the command line.
references:
  - https://github.com/redcanaryco/atomic-red-team/blob/40b77d63808dd4f4eafb83949805636735a1fd15/atomics/T1484.001/T1484.001.md
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_reg_modify_group_policy_settings.yml
author: frack113, Huntrule Team
date: 2022-08-19
tags:
  - attack.privilege-escalation
  - attack.defense-impairment
  - attack.t1484.001
logsource:
  category: process_creation
  product: windows
detection:
  selection_reg:
    - Image|endswith: \reg.exe
    - OriginalFileName: reg.exe
  selection_path:
    CommandLine|contains: \SOFTWARE\Policies\Microsoft\Windows\System
  selection_key:
    CommandLine|contains:
      - GroupPolicyRefreshTimeDC
      - GroupPolicyRefreshTimeOffsetDC
      - GroupPolicyRefreshTime
      - GroupPolicyRefreshTimeOffset
      - EnableSmartScreen
      - ShellSmartScreenLevel
  condition: all of selection_*
falsepositives:
  - Legitimate use
level: medium
license: DRL-1.1

What it detects

This rule identifies Windows process executions where reg.exe is used to modify registry values under the Group Policy System policy path. Attackers can use GPO-related policy changes to enable or alter security-relevant behavior across endpoints without deploying new binaries. The detection relies on process creation telemetry (Image/OriginalFileName and CommandLine) and matches specific Group Policy setting names within the command line.

Known false positives

  • Legitimate use

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.