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

Hunt Hypothesis

Detects execution of attacker-controlled WsmPty.xsl or WsmTxt.xsl via winrm.vbs and copied cscript.exe (can be renamed)

Detection Rule

Sigma (Original)

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

KQL (Azure Sentinel)

imProcessCreate
| where TargetProcessCommandLine contains "winrm" and ((TargetProcessCommandLine contains "format:pretty" or TargetProcessCommandLine contains "format:\"pretty\"" or TargetProcessCommandLine contains "format:\"text\"" or TargetProcessCommandLine contains "format:text") and (not((TargetProcessName startswith "C:\\Windows\\System32\\" or TargetProcessName startswith "C:\\Windows\\SysWOW64\\"))))

Required Data Sources

False Positive Guidance

• Unlikely

MITRE ATT&CK Context

• Technique: T1216 — T1216

References

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