Suspicious FileFix Execution Pattern — Sigma Rule

Rule metadata and linked tags

Author: 0xFustang, Swachchhanda Shrawan Poudel (Nextron Systems). Source status: experimental; severity: high. Source dates: 2025-11-24 / not supplied.

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

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: e60c301f36e6292ba79622e7961fdceaef9ad5f137f4f2d744cadfbd0017ae5a

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 FileFix Execution Pattern
id: b5b29e4e-31fa-4fdf-b058-296e7a1aa0c2
related:
    - id: 4fee3d51-8069-4a4c-a0f7-924fcaff2c70
      type: similar
    - id: 4be03877-d5b6-4520-85c9-a5911c0a656c
      type: obsolete
status: experimental
description: |
    Detects suspicious FileFix execution patterns where users are tricked into running malicious commands through browser file upload dialog manipulation.
    This attack typically begins when users visit malicious websites impersonating legitimate services or news platforms,
    which may display fake CAPTCHA challenges or direct instructions to open file explorer and paste clipboard content.
    The clipboard content usually contains commands that download and execute malware, such as information stealing tools.
references:
    - https://mrd0x.com/filefix-clickfix-alternative/
    - https://expel.com/blog/cache-smuggling-when-a-picture-isnt-a-thousand-words/ # phishing lure directly asking users to open file explorer and paste command
    - https://blog.checkpoint.com/research/filefix-the-new-social-engineering-attack-building-on-clickfix-tested-in-the-wild/
author: 0xFustang, Swachchhanda Shrawan Poudel (Nextron Systems)
date: 2025-11-24
tags:
    - attack.execution
    - attack.t1204.004
logsource:
    category: process_creation
    product: windows
detection:
    selection_exec_parent:
        # This is case where phishing pages trick users to paste commands in browser file upload dialog
        ParentImage|endswith:
            - '\brave.exe'
            - '\chrome.exe'
            - '\firefox.exe'
            - '\msedge.exe'
        CommandLine|contains: '#'
    selection_cli_lolbin:
        CommandLine|contains:
            - '%comspec%'
            - 'bitsadmin'
            - 'certutil'
            - 'cmd'
            - 'cscript'
            - 'curl'
            - 'finger'
            - 'mshta'
            - 'powershell'
            - 'pwsh'
            - 'regsvr32'
            - 'rundll32'
            - 'schtasks'
            - 'wget'
            - 'wscript'
    selection_cli_captcha:
        CommandLine|contains:
            - 'account'
            - 'anti-bot'
            - 'botcheck'
            - 'captcha'
            - 'challenge'
            - 'confirmation'
            - 'fraud'
            - 'human'
            - 'identification'
            - 'identificator'
            - 'identity'
            - 'robot'
            - 'validation'
            - 'verification'
            - 'verify'
    condition: selection_exec_parent and 1 of selection_cli_*
falsepositives:
    - Legitimate use of PowerShell or other utilities launched from browser extensions or automation tools
level: high

Original YAML and metadata in JSON

False positives

• Legitimate use of PowerShell or other utilities launched from browser extensions or automation tools

Source references

• https://mrd0x.com/filefix-clickfix-alternative/
• https://expel.com/blog/cache-smuggling-when-a-picture-isnt-a-thousand-words/
• https://blog.checkpoint.com/research/filefix-the-new-social-engineering-attack-building-on-clickfix-tested-in-the-wild/