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Windows PowerShell Obfuscated COM MSI Installation via WindowsInstaller.Installer

PowerShell spawning that uses WindowsInstaller.Installer COM with obfuscated strings to call InstallProduct and suppress UI.

FreeUnreviewedSigmahighv1
title: Windows PowerShell Obfuscated COM MSI Installation via WindowsInstaller.Installer
id: 83386d89-8168-4ce9-a357-a1fe9450a33a
status: experimental
description: This rule flags Windows PowerShell executions where the command line includes creation of a COM object for Windows Installer (WindowsInstaller.Installer) followed by a call to InstallProduct. It focuses on obfuscated behavior indicators in the PowerShell command such as string insertion used to construct the COM class name and runtime string manipulation to form values like URLs. Attackers use this approach to hide intent and deliver software installations with minimal user interaction by leveraging legitimate installer functionality and COM automation. The detection relies on process creation telemetry capturing PowerShell image names and command-line substrings indicating -ComObject, InstallProduct, string insertion, and UILevel setting.
references:
  - https://informationsecuritybuzz.com/the-real-danger-behind-a-simple-windows-shortcut/
  - https://redcanary.com/blog/threat-intelligence/intelligence-insights-may-2025/
  - https://www.virustotal.com/gui/file/f9710b0ba4de5fa0e7ec27da462d4d2fc6838eba83a19f23f6617a466bbad457
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_powershell_comobject_msi.yml
author: Meroujan Antonyan (vx3r), Huntrule Team
date: 2025-05-27
tags:
  - attack.stealth
  - attack.t1027.010
  - attack.t1218.007
  - attack.execution
  - attack.t1059.001
logsource:
  category: process_creation
  product: windows
detection:
  selection_img:
    - Image|endswith:
        - \powershell_ise.exe
        - \powershell.exe
        - \pwsh.exe
    - OriginalFileName:
        - PowerShell_ISE.EXE
        - PowerShell.EXE
        - pwsh.dll
  selection_cli:
    CommandLine|contains|all:
      - -ComObject
      - InstallProduct(
      - .Insert(
      - UILevel
  condition: all of selection_*
falsepositives:
  - Unknown
level: high
license: DRL-1.1
related:
  - id: 7b6a7418-3afc-11f0-aff4-000d3abf478c
    type: derived

What it detects

This rule flags Windows PowerShell executions where the command line includes creation of a COM object for Windows Installer (WindowsInstaller.Installer) followed by a call to InstallProduct. It focuses on obfuscated behavior indicators in the PowerShell command such as string insertion used to construct the COM class name and runtime string manipulation to form values like URLs. Attackers use this approach to hide intent and deliver software installations with minimal user interaction by leveraging legitimate installer functionality and COM automation. The detection relies on process creation telemetry capturing PowerShell image names and command-line substrings indicating -ComObject, InstallProduct, string insertion, and UILevel setting.

Known false positives

  • Unknown

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