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Windows PowerShell Module Obfuscated Invocation (VAR++ LAUNCHER pattern)

Identifies obfuscated PowerShell module payloads matching a VAR++ LAUNCHER-style invocation pattern.

FreeUnreviewedSigmahighv1
title: Windows PowerShell Module Obfuscated Invocation (VAR++ LAUNCHER pattern)
id: 68c97439-e8d6-4850-befe-b47235a9fdca
related:
  - id: e54f5149-6ba3-49cf-b153-070d24679126
    type: derived
  - id: f3c89218-8c3d-4ba9-9974-f1d8e6a1b4a6
    type: derived
status: test
description: This rule flags PowerShell module content that matches an obfuscation-style invocation pattern using repeated set constructs and formatted strings consistent with a VAR++ LAUNCHER launcher. Attackers often rely on obfuscation to hinder static analysis and signature-based detections while still executing commands. The detection relies on PowerShell module telemetry field matching on the Payload content with a case-insensitive regular expression.
references:
  - https://github.com/SigmaHQ/sigma/issues/1009
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/powershell/powershell_module/posh_pm_invoke_obfuscation_via_var.yml
author: Timur Zinniatullin, oscd.community, Huntrule Team
date: 2020-10-13
modified: 2024-04-05
tags:
  - attack.stealth
  - attack.t1027
  - attack.execution
  - attack.t1059.001
logsource:
  product: windows
  category: ps_module
  definition: 0ad03ef1-f21b-4a79-8ce8-e6900c54b65b
detection:
  selection_4103:
    Payload|re: (?i)&&set.*(\{\d\}){2,}\\"\s+?-f.*&&.*cmd.*/c
  condition: selection_4103
falsepositives:
  - Unknown
level: high
license: DRL-1.1

What it detects

This rule flags PowerShell module content that matches an obfuscation-style invocation pattern using repeated set constructs and formatted strings consistent with a VAR++ LAUNCHER launcher. Attackers often rely on obfuscation to hinder static analysis and signature-based detections while still executing commands. The detection relies on PowerShell module telemetry field matching on the Payload content with a case-insensitive regular expression.

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.