Suspicious PowerShell Module Usage with Hidden/Encoded Execution Parameters on Windows

Flags hidden or encoded PowerShell invocations that decode/execute code or download-and-execute patterns, while filtering a Chocolatey installer snippet.

FreeReviewedSigma · High · v2

Product: windows
Category: ps_module
Author: Florian Roth (Nextron Systems), Jonhnathan Ribeiro (SigmaHQ), DRL 1.1
Published: 2017-03-05
Updated: 2026-07-31

Analysis Detection

ATT&CK techniques

Execution

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

What it detects

This rule flags PowerShell executions that include hidden or non-interactive invocation parameters combined with encoded or staged command execution patterns. It matters because attackers often use PowerShell to run payloads covertly via Base64 decoding, IEX-based execution, or encoded command options to reduce visibility. The detection relies on Windows telemetry containing PowerShell module ContextInfo strings with specific combinations of flags and command fragments (e.g., -nop, hidden windowing, -c with Convert.FromBase64String or iex/New-Object).

Reporting behind it

Related detections9 linkedT1059.001 — drag to rearrange

Suspicious Script Host Spawning Hidden PowerShell (via process_creation)

Suspicious PowerShell Reflective Assembly Load With GZip Decompression (via process_creation)

Suspicious PowerShell Invoke-Expression with Replace Obfuscation

Suspicious PowerShell Archive Extraction to AppData Roaming

Malicious PowerShell Spawned by Masqueraded NVIDIA GeForce Experience Binary

Suspicious PowerShell Hidden Unrestricted Execution via ClickFix

Suspicious PowerShell Spawned by cscript in Script Chain

Suspicious Script Interpreter Spawned by Explorer via ClickFix Run Dialog (via process_creation)

Suspicious PowerShell Download Cradle via ClickFix Fake CAPTCHA (via process_creation)

Suspicious PowerShell Module Usage with Hidden/Encoded Execution Parameters on Windows

Pivot detection · T1059.001 · 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.

suspicious-powershell-module-execution-parameters-for-encoded-hidden-code-8ff28fdd

title: Suspicious PowerShell Module Usage with Hidden/Encoded Execution Parameters on Windows
id: df447db8-de97-4cfb-8744-f164d7e3550f
related:
  - id: fce5f582-cc00-41e1-941a-c6fabf0fdb8c
    type: obsolete
  - id: ae7fbf8e-f3cb-49fd-8db4-5f3bed522c71
    type: similar
  - id: 536e2947-3729-478c-9903-745aaffe60d2
    type: similar
  - id: 8ff28fdd-e2fa-4dfa-aeda-ef3d61c62090
    type: derived
status: test
description: This rule flags PowerShell executions that include hidden or non-interactive invocation parameters combined with encoded or staged command execution patterns. It matters because attackers often use PowerShell to run payloads covertly via Base64 decoding, IEX-based execution, or encoded command options to reduce visibility. The detection relies on Windows telemetry containing PowerShell module ContextInfo strings with specific combinations of flags and command fragments (e.g., -nop, hidden windowing, -c with Convert.FromBase64String or iex/New-Object).
references:
  - Internal Research
  - https://github.com/HackTricks-wiki/hacktricks/blob/e4c7b21b8f36c97c35b7c622732b38a189ce18f7/src/windows-hardening/windows-local-privilege-escalation/privilege-escalation-with-autorun-binaries.md
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/powershell/powershell_module/posh_pm_susp_invocation_specific.yml
author: Florian Roth (Nextron Systems), Jonhnathan Ribeiro, Huntrule Team
date: 2017-03-05
modified: 2025-02-17
tags:
  - attack.execution
  - attack.t1059.001
logsource:
  product: windows
  category: ps_module
  definition: 0ad03ef1-f21b-4a79-8ce8-e6900c54b65b
detection:
  selection_convert_b64:
    ContextInfo|contains|all:
      - -nop
      - " -w "
      - hidden
      - " -c "
      - "[Convert]::FromBase64String"
  selection_iex:
    ContextInfo|contains|all:
      - " -w "
      - hidden
      - -noni
      - -nop
      - " -c "
      - iex
      - New-Object
  selection_enc:
    ContextInfo|contains|all:
      - " -w "
      - hidden
      - -ep
      - bypass
      - -Enc
  selection_reg:
    ContextInfo|contains|all:
      - powershell
      - reg
      - add
    ContextInfo|contains:
      - \software\microsoft\windows\currentversion\run
      - \software\wow6432node\microsoft\windows\currentversion\run
      - \software\microsoft\windows\currentversion\policies\explorer\run
  selection_webclient:
    ContextInfo|contains|all:
      - bypass
      - -noprofile
      - -windowstyle
      - hidden
      - new-object
      - system.net.webclient
      - .download
  selection_iex_webclient:
    ContextInfo|contains|all:
      - iex
      - New-Object
      - Net.WebClient
      - .Download
  filter_chocolatey:
    ContextInfo|contains:
      - (New-Object System.Net.WebClient).DownloadString('https://community.chocolatey.org/install.ps1
      - Write-ChocolateyWarning
  condition: 1 of selection_* and not 1 of filter_*
falsepositives:
  - Unknown
level: high
license: DRL-1.1

Convert

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

SplunkSPL