PowerShell Downgrade Attempts via -Version 2 on Windows Process Creation

Alerts on PowerShell executions specifying a -Version 2 argument, consistent with potential downgrade attempts.

FreeReviewedSigma · Medium · v1

Product: windows
Category: process_creation
Author: Harish Segar (rule) (SigmaHQ), DRL 1.1
Published: 2020-03-20
Updated: 2026-07-30

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 processes where the command line includes indications of using the -version parameter set to 2. Attackers may downgrade the PowerShell engine version to change available defenses and behavior, including reducing protections that depend on newer versions. It relies on Windows process creation telemetry, specifically the process image path ending in powershell.exe and matching command-line substrings that contain version 2 arguments.

Reporting behind it

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PowerShell Downgrade Attempts via -Version 2 on Windows Process Creation

Pivot detection · T1059.001 · 9 related

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

powershell-downgrade-attempts-via-version-2-on-windows-process-creation-b3512211

title: PowerShell Downgrade Attempts via -Version 2 on Windows Process Creation
id: 679911ce-c6f1-444b-8447-64f363cbff23
related:
  - id: 6331d09b-4785-4c13-980f-f96661356249
    type: derived
  - id: b3512211-c67e-4707-bedc-66efc7848863
    type: derived
status: test
description: This rule flags PowerShell processes where the command line includes indications of using the -version parameter set to 2. Attackers may downgrade the PowerShell engine version to change available defenses and behavior, including reducing protections that depend on newer versions. It relies on Windows process creation telemetry, specifically the process image path ending in powershell.exe and matching command-line substrings that contain version 2 arguments.
references:
  - http://www.leeholmes.com/blog/2017/03/17/detecting-and-preventing-powershell-downgrade-attacks/
  - https://github.com/r00t-3xp10it/hacking-material-books/blob/43cb1e1932c16ff1f58b755bc9ab6b096046853f/obfuscation/simple_obfuscation.md#bypass-or-avoid-amsi-by-version-downgrade-
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_powershell_downgrade_attack.yml
author: Harish Segar (rule), Huntrule Team
date: 2020-03-20
modified: 2023-01-04
tags:
  - attack.execution
  - attack.t1059.001
logsource:
  category: process_creation
  product: windows
detection:
  selection:
    Image|endswith: \powershell.exe
    CommandLine|contains:
      - " -version 2 "
      - " -versio 2 "
      - " -versi 2 "
      - " -vers 2 "
      - " -ver 2 "
      - " -ve 2 "
      - " -v 2 "
  condition: selection
falsepositives:
  - Unknown
level: medium
license: DRL-1.1

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