Forfiles.EXE Child Process Masquerading — Sigma Rule

Rule metadata and linked tags

Author: Nasreddine Bencherchali (Nextron Systems), Anish Bogati. Source status: test; severity: high. Source dates: 2024-01-05 / not supplied.

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

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: ed5bdeed968237e53e1a7dbed423c3bcc5e6186d77a0147f2b4db8c5c48f222c

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: Forfiles.EXE Child Process Masquerading
id: f53714ec-5077-420e-ad20-907ff9bb2958
status: test
description: |
    Detects the execution of "forfiles" from a non-default location, in order to potentially spawn a custom "cmd.exe" from the current working directory.
references:
    - https://www.hexacorn.com/blog/2023/12/31/1-little-known-secret-of-forfiles-exe/
author: Nasreddine Bencherchali (Nextron Systems), Anish Bogati
date: 2024-01-05
tags:
    - attack.stealth
    - attack.t1036
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        # Notes:
        #   - The parent must not have CLI options
        #   - The Child Image must be named "cmd" as its hardcoded in the "forfiles" binary
        #   - The Child CLI will always contains "/c echo" as its hardcoded in the original "forfiles" binary
        ParentCommandLine|endswith:
            - '.exe'
            - '.exe"'
        Image|endswith: '\cmd.exe'
        CommandLine|startswith: '/c echo "'
    filter_main_parent_not_sys:
        ParentImage|contains:
            - ':\Windows\System32\'
            - ':\Windows\SysWOW64\'
        ParentImage|endswith: '\forfiles.exe'
        Image|contains:
            - ':\Windows\System32\'
            - ':\Windows\SysWOW64\'
        Image|endswith: '\cmd.exe'
    condition: selection and not 1 of filter_main_*
falsepositives:
    - Unknown
level: high

Original YAML and metadata in JSON

False positives

• Unknown

Source references

• https://www.hexacorn.com/blog/2023/12/31/1-little-known-secret-of-forfiles-exe/