PowerShell Obfuscation Delivered via Stdin Using Set-and-Invoke Pattern

Detects obfuscated PowerShell script blocks that use chained stdin/environment/input patterns.

FreeReviewedSigma · High · v2

Product: windows
Category: ps_script
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 script block text that matches an obfuscated “set … && set … (environment|invoke|${input}) … && … " pattern, which is commonly used to hide malicious intent while still executing. Attackers may use stdin-driven and chained assignments/invocations to evade straightforward inspection and blend execution with environment/input handling. The detection relies on Script Block Logging telemetry that captures the full script block text executed in PowerShell.

Reporting behind it

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Malicious Non-Interactive Encoded PowerShell Stager (via process_creation)

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PowerShell Encoded or Download-Cradle Command Line (via process_creation)

Obfuscated Encoded PowerShell Payload Deployed - PowerShell (via powershell)

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PowerShell Obfuscation Delivered via Stdin Using Set-and-Invoke 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-obfuscation-through-stdin-via-scriptblocktext-86b896ba

title: PowerShell Obfuscation Delivered via Stdin Using Set-and-Invoke Pattern
id: 9cc577c9-de1c-4b41-a05f-2a3c9d1b2c95
status: test
description: This rule flags PowerShell script block text that matches an obfuscated “set … && set … (environment|invoke|${input}) … && … " pattern, which is commonly used to hide malicious intent while still executing. Attackers may use stdin-driven and chained assignments/invocations to evade straightforward inspection and blend execution with environment/input handling. The detection relies on Script Block Logging telemetry that captures the full script block text executed in PowerShell.
references:
  - https://github.com/SigmaHQ/sigma/issues/1009
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/powershell/powershell_script/posh_ps_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_script
  definition: "Requirements: Script Block Logging must be enabled"
detection:
  selection_4104:
    ScriptBlockText|re: (?i)(set).*&&\s?set.*(environment|invoke|\$\{?input).*&&.*"
  condition: selection_4104
falsepositives:
  - Unknown
level: high
license: DRL-1.1
related:
  - id: 86b896ba-ffa1-4fea-83e3-ee28a4c915c7
    type: derived

Convert

This rule as a query you can run. Uses no unlock credit.

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