Windows PowerShell Script Installs and Configures PowerShell Web Access (PSWA)

Detects PowerShell Web Access installation and web authorization configuration from Windows PowerShell script blocks.

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windows-powershell-script-installs-and-configures-powershell-web-access-pswa-5f9c7f1a

title: Windows PowerShell Script Installs and Configures PowerShell Web Access (PSWA)
id: ce0e85f5-dcd3-4158-ab75-039a44bf32ba
status: test
description: This rule flags PowerShell script activity that installs WindowsPowerShellWebAccess, creates a PSWA web application, and configures broad authorization rules. Attackers can use this to establish remote access through PowerShell Web Access for follow-on execution or abuse. The detection relies on Script Block Logging telemetry matching specific command strings within PowerShell ScriptBlockText.
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
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/powershell/powershell_script/posh_ps_powershell_web_access_installation.yml
author: Michael Haag, Huntrule Team
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
license: DRL-1.1
related:
  - id: 5f9c7f1a-7c21-4c39-b2f3-8d8006e0e51f
    type: derived

What it detects

This rule flags PowerShell script activity that installs WindowsPowerShellWebAccess, creates a PSWA web application, and configures broad authorization rules. Attackers can use this to establish remote access through PowerShell Web Access for follow-on execution or abuse. The detection relies on Script Block Logging telemetry matching specific command strings within PowerShell ScriptBlockText.

Known false positives

Legitimate PowerShell Web Access installations by administrators

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