Suspicious XOR Encoded PowerShell Command — Sigma Rule

Rule metadata and linked tags

Author: Sami Ruohonen, Harish Segar, Tim Shelton, Teymur Kheirkhabarov, Vasiliy Burov, oscd.community, Nasreddine Bencherchali. Source status: test; severity: medium. Source dates: 2018-09-05 / 2023-01-30.

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

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 06e0d8f74735fc5b1f15d0c244023addd14d22486027c6866e837e1b79ca2f03

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: Suspicious XOR Encoded PowerShell Command
id: bb780e0c-16cf-4383-8383-1e5471db6cf9
related:
    - id: 5b572dcf-254b-425c-a8c5-d9af6bea35a6
      type: obsolete
status: test
description: Detects presence of a potentially xor encoded powershell command
references:
    - https://speakerdeck.com/heirhabarov/hunting-for-powershell-abuse?slide=65
    - https://redcanary.com/blog/yellow-cockatoo/
    - https://zero2auto.com/2020/05/19/netwalker-re/
    - https://mez0.cc/posts/cobaltstrike-powershell-exec/
author: Sami Ruohonen, Harish Segar, Tim Shelton, Teymur Kheirkhabarov, Vasiliy Burov, oscd.community, Nasreddine Bencherchali
date: 2018-09-05
modified: 2023-01-30
tags:
    - attack.execution
    - attack.stealth
    - attack.t1059.001
    - attack.t1140
    - attack.t1027
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - Image|endswith:
              - '\powershell.exe'
              - '\pwsh.exe'
        - OriginalFileName:
              - 'PowerShell.EXE'
              - 'pwsh.dll'
        - Description: 'Windows PowerShell'
        - Product: 'PowerShell Core 6'
    selection_cli_xor:
        CommandLine|contains: 'bxor'
    selection_cli_other:
        CommandLine|contains:
            - 'ForEach'
            - 'for('
            - 'for '
            - '-join '
            - "-join'"
            - '-join"'
            - '-join`'
            - '::Join'
            - '[char]'
    condition: all of selection_*
falsepositives:
    - Unknown
level: medium

Original YAML and metadata in JSON

False positives

• Unknown

Source references

• https://speakerdeck.com/heirhabarov/hunting-for-powershell-abuse?slide=65
• https://redcanary.com/blog/yellow-cockatoo/
• https://zero2auto.com/2020/05/19/netwalker-re/
• https://mez0.cc/posts/cobaltstrike-powershell-exec/