Modify Group Policy Settings - ScriptBlockLogging

Status: test
Severity: medium
Log source: category ps_script, 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
PowerShell	Event ID 4104: Creating Scriptblock text (MessageNumber of MessageTotal).

Rule body

title: Modify Group Policy Settings - ScriptBlockLogging
id: b7216a7d-687e-4c8d-82b1-3080b2ad961f
related:
    - id: ada4b0c4-758b-46ac-9033-9004613a150d
      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:
    product: windows
    category: ps_script
    definition: 'Requirements: Script Block Logging must be enabled'
detection:
    selection_path:
        ScriptBlockText|contains: \SOFTWARE\Policies\Microsoft\Windows\System
    selection_key:
        ScriptBlockText|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_path`

selection_path:
    ScriptBlockText|contains: \SOFTWARE\Policies\Microsoft\Windows\System

Stage 2: `selection_key`

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

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`ScriptBlockText`	match	`EnableSmartScreen` `GroupPolicyRefreshTime` `GroupPolicyRefreshTimeDC` `GroupPolicyRefreshTimeOffset` `GroupPolicyRefreshTimeOffsetDC` `ShellSmartScreenLevel` `\SOFTWARE\Policies\Microsoft\Windows\System`	`field:"ScriptBlockText" kind:match`

Modify Group Policy Settings - ScriptBlockLogging

Known false positives

MITRE ATT&CK coverage

Telemetry coverage

Rule body

Stages and Predicates

Stage 0: condition

Stage 1: selection_path

Stage 2: selection_key

Indicators

Stage 0: `condition`

Stage 1: `selection_path`

Stage 2: `selection_key`