Potential PowerShell Downgrade Attack — Sigma Rule

Rule metadata and linked tags

Author: Harish Segar (rule). Source status: test; severity: medium. Source dates: 2020-03-20 / 2023-01-04.

{
  "category": "process_creation",
  "product": "windows"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 996dcaba3cbb61198b6ebbc6dfc3b9dda0e935ab3343430e62a43ec6d58e052f

Detection logic

Original source YAML. Source-tag agreement is not proof of complete semantic coverage. This rule has not been compiled for a SIEM backend or validated against live telemetry here.

title: Potential PowerShell Downgrade Attack
id: b3512211-c67e-4707-bedc-66efc7848863
related:
    - id: 6331d09b-4785-4c13-980f-f96661356249
      type: derived
status: test
description: Detects PowerShell downgrade attack by comparing the host versions with the actually used engine version 2.0
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-
author: Harish Segar (rule)
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

Original YAML and metadata in JSON

False positives

• Unknown

Source 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-