PowerShell Web Access Installation - PsScript — Sigma Rule

Rule metadata and linked tags

Author: Michael Haag. Source status: test; severity: high. Source dates: 2024-09-03 / not supplied.

{
  "product": "windows",
  "category": "ps_script",
  "definition": "Requirements: Script Block Logging must be enabled"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 995bb2ba86649e4244cbf8e69d1dc594427265fc917084acd6b910b4b099ff9a

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: PowerShell Web Access Installation - PsScript
id: 5f9c7f1a-7c21-4c39-b2f3-8d8006e0e51f
status: test
description: Detects the installation and configuration of PowerShell Web Access, which could be used for remote access and potential abuse
references:
    - https://docs.microsoft.com/en-us/powershell/module/powershellwebaccess/install-pswawebapplication
    - https://www.cisa.gov/news-events/cybersecurity-advisories/aa24-241a
    - https://gist.github.com/MHaggis/7e67b659af9148fa593cf2402edebb41
author: Michael Haag
date: 2024-09-03
tags:
    - attack.persistence
    - attack.execution
    - attack.t1059.001
logsource:
    product: windows
    category: ps_script
    definition: 'Requirements: Script Block Logging must be enabled'
detection:
    selection_install:
        ScriptBlockText|contains: 'Install-WindowsFeature WindowsPowerShellWebAccess'
    selection_config:
        ScriptBlockText|contains: 'Install-PswaWebApplication'
    selection_auth:
        ScriptBlockText|contains|all:
            - 'Add-PswaAuthorizationRule'
            - '-UserName *'
            - '-ComputerName *'
    condition: 1 of selection_*
falsepositives:
    - Legitimate PowerShell Web Access installations by administrators
level: high

Original YAML and metadata in JSON

False positives

• Legitimate PowerShell Web Access installations by administrators

Source references

• https://docs.microsoft.com/en-us/powershell/module/powershellwebaccess/install-pswawebapplication
• https://www.cisa.gov/news-events/cybersecurity-advisories/aa24-241a
• https://gist.github.com/MHaggis/7e67b659af9148fa593cf2402edebb41