PowerShell Module: Obfuscated Script Execution via Stdin Pattern

Detects obfuscated PowerShell module payloads using chained set and stdin/input invoke patterns.

FreeReviewedSigma · High · v2

Product: windows
Category: ps_module
Author: Nikita Nazarov, oscd.community (SigmaHQ), DRL 1.1
Published: 2020-10-12
Updated: 2026-07-31

ATT&CK techniques

Execution → Defense Evasion

Recon
Resource Dev
Initial Access
Execution
- T1059.001PowerShell
Persistence
Priv Esc
Defense Evasion
- T1027Obfuscated Files or Information
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule flags PowerShell module activity containing a string pattern consistent with obfuscated script execution that chains operations using "set" and then references environment/input execution constructs. Attackers often use this style to hinder static analysis and execute payloads indirectly through stdin-related input handling. The detection relies on telemetry fields that capture the PowerShell payload content and match it against the specified case-insensitive regular expression.

Reporting behind it

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PowerShell Module: Obfuscated Script Execution via Stdin Pattern

Pivot detection · T1027 · 9 related

Changelog

v2
Candidate ingested via manual entry.2026-07-31
v1
No changelog recorded for this version.2026-07-30

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

powershell-module-obfuscated-stdin-invoke-via-chained-set-and-invoke-expressions-c72aca44

title: "PowerShell Module: Obfuscated Script Execution via Stdin Pattern"
id: 2981abae-a6ca-49ad-ab24-adac93d5ba50
related:
  - id: 86b896ba-ffa1-4fea-83e3-ee28a4c915c7
    type: derived
  - id: c72aca44-8d52-45ad-8f81-f96c4d3c755e
    type: derived
status: test
description: This rule flags PowerShell module activity containing a string pattern consistent with obfuscated script execution that chains operations using "set" and then references environment/input execution constructs. Attackers often use this style to hinder static analysis and execute payloads indirectly through stdin-related input handling. The detection relies on telemetry fields that capture the PowerShell payload content and match it against the specified 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_stdin.yml
author: Nikita Nazarov, oscd.community, Huntrule Team
date: 2020-10-12
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).*&&\s?set.*(environment|invoke|\$?\{?input).*&&.*"
  condition: selection_4103
falsepositives:
  - Unknown
level: high
license: DRL-1.1

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