Modify Group Policy Settings

Status: test
Severity: medium
Log source: category process_creation, product windows
Author: frack113
Source: github.com/SigmaHQ/sigma

Detect malicious GPO modifications can be used to implement many other malicious behaviors.

Known false positives

Legitimate use

MITRE ATT&CK coverage

Tactic	Techniques
Privilege Escalation	`T1484.001` Domain or Tenant Policy Modification: Group Policy Modification
Defense Impairment	`T1484.001` Domain or Tenant Policy Modification: Group Policy Modification

Telemetry coverage

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

Rule body

title: Modify Group Policy Settings
id: ada4b0c4-758b-46ac-9033-9004613a150d
related:
    - id: b7216a7d-687e-4c8d-82b1-3080b2ad961f
      type: similar
status: test
description: Detect malicious GPO modifications can be used to implement many other malicious behaviors.
references:
    - https://github.com/redcanaryco/atomic-red-team/blob/40b77d63808dd4f4eafb83949805636735a1fd15/atomics/T1484.001/T1484.001.md
author: frack113
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

Stages and Predicates

Stage 0: `condition`

all of selection_*

Stage 1: `selection_reg`

selection_reg:
    - Image|endswith: '\reg.exe'
    - OriginalFileName: 'reg.exe'

Stage 2: `selection_path`

selection_path:
    CommandLine|contains: '\SOFTWARE\Policies\Microsoft\Windows\System'

Stage 3: `selection_key`

selection_key:
    CommandLine|contains:
        - GroupPolicyRefreshTimeDC
        - GroupPolicyRefreshTimeOffsetDC
        - GroupPolicyRefreshTime
        - GroupPolicyRefreshTimeOffset
        - EnableSmartScreen
        - ShellSmartScreenLevel

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`CommandLine`	match	`EnableSmartScreen` `GroupPolicyRefreshTime` `GroupPolicyRefreshTimeDC` `GroupPolicyRefreshTimeOffset` `GroupPolicyRefreshTimeOffsetDC` `ShellSmartScreenLevel` `\SOFTWARE\Policies\Microsoft\Windows\System`	`field:"CommandLine" kind:match`
`Image`	ends_with	`\reg.exe` corpus 58 (sigma 58)	`field:"Image" kind:ends_with value:"\reg.exe"`
`OriginalFileName`	eq	`reg.exe` corpus 43 (sigma 32, splunk 8, elastic 3)	`field:"OriginalFileName" kind:eq value:"reg.exe"`

Modify Group Policy Settings

Known false positives

MITRE ATT&CK coverage

Telemetry coverage

Rule body

Stages and Predicates

Stage 0: condition

Stage 1: selection_reg

Stage 2: selection_path

Stage 3: selection_key

Indicators

Stage 0: `condition`

Stage 1: `selection_reg`

Stage 2: `selection_path`

Stage 3: `selection_key`