Potential PowerShell Execution Policy Tampering - ProcCreation

Status: test
Severity: high
Log source: category process_creation, product windows
Author: Nasreddine Bencherchali (Nextron Systems)
Source: github.com/SigmaHQ/sigma

Detects changes to the PowerShell execution policy registry key in order to bypass signing requirements for script execution from the CommandLine

MITRE ATT&CK coverage

Tactic	Techniques
Defense Impairment	No specific technique

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 1: Process creation
Security-Auditing	Event ID 4688: A new process has been created.

Rule body

title: Potential PowerShell Execution Policy Tampering - ProcCreation
id: cf2e938e-9a3e-4fe8-a347-411642b28a9f
related:
    - id: fad91067-08c5-4d1a-8d8c-d96a21b37814 # ProcCreation Registry
      type: similar
    - id: 87e3c4e8-a6a8-4ad9-bb4f-46e7ff99a180 # ProcCreation Cmdlet
      type: similar
    - id: 61d0475c-173f-4844-86f7-f3eebae1c66b # PowerShell ScriptBlock
      type: similar
status: test
description: Detects changes to the PowerShell execution policy registry key in order to bypass signing requirements for script execution from the CommandLine
references:
    - https://learn.microsoft.com/de-de/powershell/module/microsoft.powershell.security/set-executionpolicy?view=powershell-7.3
author: Nasreddine Bencherchali (Nextron Systems)
date: 2023-01-11
tags:
    - attack.defense-impairment
logsource:
    product: windows
    category: process_creation
detection:
    selection_path:
        CommandLine|contains:
            - '\ShellIds\Microsoft.PowerShell\ExecutionPolicy'
            - '\Policies\Microsoft\Windows\PowerShell\ExecutionPolicy'
    selection_values:
        CommandLine|contains:
            - 'Bypass'
            - 'RemoteSigned'
            - 'Unrestricted'
    condition: all of selection_*
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: `condition`

all of selection_*

Stage 1: `selection_path`

selection_path:
    CommandLine|contains:
        - '\ShellIds\Microsoft.PowerShell\ExecutionPolicy'
        - '\Policies\Microsoft\Windows\PowerShell\ExecutionPolicy'

Stage 2: `selection_values`

selection_values:
    CommandLine|contains:
        - 'Bypass'
        - 'RemoteSigned'
        - 'Unrestricted'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`CommandLine`	match	`Bypass` corpus 6 (sigma 6) `RemoteSigned` `Unrestricted` corpus 2 (sigma 2) `\Policies\Microsoft\Windows\PowerShell\ExecutionPolicy` `\ShellIds\Microsoft.PowerShell\ExecutionPolicy`	`field:"CommandLine" kind:match`

Potential PowerShell Execution Policy Tampering - ProcCreation

MITRE ATT&CK coverage

Telemetry coverage

Rule body

Stages and Predicates

Stage 0: condition

Stage 1: selection_path

Stage 2: selection_values

Indicators

Stage 0: `condition`

Stage 1: `selection_path`

Stage 2: `selection_values`