AWL Bypass with Winrm.vbs and Malicious WsmPty.xsl/WsmTxt.xsl — Sigma Rule

Rule metadata and linked tags

Author: Julia Fomina, oscd.community. Source status: test; severity: medium. Source dates: 2020-10-06 / 2022-10-09.

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

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 4e32badc4e851f3bf28999193671c7c46cb797d0dbc36b31cf05543adce79d65

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: AWL Bypass with Winrm.vbs and Malicious WsmPty.xsl/WsmTxt.xsl
id: 074e0ded-6ced-4ebd-8b4d-53f55908119d
status: test
description: Detects execution of attacker-controlled WsmPty.xsl or WsmTxt.xsl via winrm.vbs and copied cscript.exe (can be renamed)
references:
    - https://posts.specterops.io/application-whitelisting-bypass-and-arbitrary-unsigned-code-execution-technique-in-winrm-vbs-c8c24fb40404
author: Julia Fomina, oscd.community
date: 2020-10-06
modified: 2022-10-09
tags:
    - attack.stealth
    - attack.t1216
logsource:
    category: process_creation
    product: windows
detection:
    contains_format_pretty_arg:
        CommandLine|contains:
            - 'format:pretty'
            - 'format:"pretty"'
            - 'format:"text"'
            - 'format:text'
    image_from_system_folder:
        Image|startswith:
            - 'C:\Windows\System32\'
            - 'C:\Windows\SysWOW64\'
    contains_winrm:
        CommandLine|contains: 'winrm'
    condition: contains_winrm and (contains_format_pretty_arg and not image_from_system_folder)
falsepositives:
    - Unlikely
level: medium

Original YAML and metadata in JSON

False positives

• Unlikely

Source references

• https://posts.specterops.io/application-whitelisting-bypass-and-arbitrary-unsigned-code-execution-technique-in-winrm-vbs-c8c24fb40404