PowerShell ScriptBlock uses rundll32 with shell32.dll and obfuscated invoke/comspec/iex

Flags PowerShell script blocks containing rundll32/shell32.dll execution strings alongside invoke/iex/comspec patterns.

FreeReviewedSigma · High · v2

Product: windows
Category: ps_script
Author: Nikita Nazarov, oscd.community (SigmaHQ), DRL 1.1
Published: 2019-10-08
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 matches PowerShell script block content that includes multiple indicators of rundll32-based obfuscation, specifically references to rundll32, shell32.dll, and shellexec_rundll along with command-composition markers. It further requires additional keywords consistent with execution and payload staging (value, invoke, comspec, and iex). Attackers may use this pattern to obscure process launch and execution flow; the detection relies on Script Block Logging telemetry that captures ScriptBlockText.

Reporting behind it

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PowerShell ScriptBlock uses rundll32 with shell32.dll and obfuscated invoke/comspec/iex

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-using-rundll32-and-shell32-dll-via-script-block-logging-a5a30a6e

title: PowerShell ScriptBlock uses rundll32 with shell32.dll and obfuscated invoke/comspec/iex
id: e1c3d2a0-fbb7-4c0e-be21-90a4d30bb48a
status: test
description: This rule matches PowerShell script block content that includes multiple indicators of rundll32-based obfuscation, specifically references to rundll32, shell32.dll, and shellexec_rundll along with command-composition markers. It further requires additional keywords consistent with execution and payload staging (value, invoke, comspec, and iex). Attackers may use this pattern to obscure process launch and execution flow; the detection relies on Script Block Logging telemetry that captures ScriptBlockText.
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_use_rundll32.yml
author: Nikita Nazarov, oscd.community, Huntrule Team
date: 2019-10-08
modified: 2022-11-29
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|contains|all:
      - "&&"
      - rundll32
      - shell32.dll
      - shellexec_rundll
    ScriptBlockText|contains:
      - value
      - invoke
      - comspec
      - iex
  condition: selection_4104
falsepositives:
  - Unknown
level: high
license: DRL-1.1
related:
  - id: a5a30a6e-75ca-4233-8b8c-42e0f2037d3b
    type: derived

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