VMToolsd Suspicious Child Process — Sigma Rule

Rule metadata and linked tags

Author: bohops, Bhabesh Raj. Source status: test; severity: high. Source dates: 2021-10-08 / 2023-07-25.

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

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 7f9748d35baa0c893434017980e27813582f9e629723972e92bfd61fd5ab0061

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: VMToolsd Suspicious Child Process
id: 5687f942-867b-4578-ade7-1e341c46e99a
status: test
description: Detects suspicious child process creations of VMware Tools process which may indicate persistence setup
references:
    - https://bohops.com/2021/10/08/analyzing-and-detecting-a-vmtools-persistence-technique/
    - https://user-images.githubusercontent.com/61026070/136518004-b68cce7d-f9b8-4e9a-9b7b-53b1568a9a94.png
    - https://github.com/vmware/open-vm-tools/blob/master/open-vm-tools/tools.conf
author: bohops, Bhabesh Raj
date: 2021-10-08
modified: 2023-07-25
tags:
    - attack.execution
    - attack.persistence
    - attack.t1059
logsource:
    category: process_creation
    product: windows
detection:
    selection_parent:
        ParentImage|endswith: '\vmtoolsd.exe'
    selection_img:
        - Image|endswith:
              - '\cmd.exe'
              - '\cscript.exe'
              - '\mshta.exe'
              - '\powershell.exe'
              - '\pwsh.exe'
              - '\regsvr32.exe'
              - '\rundll32.exe'
              - '\wscript.exe'
        - OriginalFileName:
              - 'Cmd.Exe'
              - 'cscript.exe'
              - 'MSHTA.EXE'
              - 'PowerShell.EXE'
              - 'pwsh.dll'
              - 'REGSVR32.EXE'
              - 'RUNDLL32.EXE'
              - 'wscript.exe'
    filter_main_vmwaretools_script:
        Image|endswith: '\cmd.exe'
        CommandLine|contains:
            - '\VMware\VMware Tools\poweron-vm-default.bat'
            - '\VMware\VMware Tools\poweroff-vm-default.bat'
            - '\VMware\VMware Tools\resume-vm-default.bat'
            - '\VMware\VMware Tools\suspend-vm-default.bat'
    filter_main_empty:
        Image|endswith: '\cmd.exe'
        CommandLine: ''
    filter_main_null:
        Image|endswith: '\cmd.exe'
        CommandLine: null
    condition: all of selection* and not 1 of filter_main_*
falsepositives:
    - Legitimate use by VM administrator
level: high

Original YAML and metadata in JSON

False positives

• Legitimate use by VM administrator

Source references

• https://bohops.com/2021/10/08/analyzing-and-detecting-a-vmtools-persistence-technique/
• https://user-images.githubusercontent.com/61026070/136518004-b68cce7d-f9b8-4e9a-9b7b-53b1568a9a94.png
• https://github.com/vmware/open-vm-tools/blob/master/open-vm-tools/tools.conf