Suspicious Explorer Process with Whitespace Padding - ClickFix/FileFix

SIGMA detection rule by Swachchhanda Shrawan Poudel (Nextron Systems) · GPL-2.0

Detects process creation with suspicious whitespace padding followed by a '#' character, which may indicate ClickFix or FileFix techniques used to conceal malicious commands from visual inspection. ClickFix and FileFix are social engineering attack techniques where adversaries distribute phishing documents or malicious links that deceive users into opening the Windows Run dialog box or File Explorer search bar. The victims are then instructed to paste commands from their clipboard, which contain extensive whitespace padding using various Unicode space characters to push the actual malicious command far to the right, effectively hiding it from immediate view.

title: Suspicious Explorer Process with Whitespace Padding - ClickFix/FileFix
id: ed6d814e-9b25-6213-526d-92e0d4cca625
related:
    - id: 8f2a5c3d-9e4b-4a7c-8d1f-2e5a6b9c3d7e
      type: similar
    - id: 7a1b4c5e-8f3d-4b9a-7c2e-1f4a5b8c6d9e
      type: similar
    - id: 3ae9974a-eb09-4044-8e70-8980a50c12c8
      type: derived
status: experimental
description: |
    Detects process creation with suspicious whitespace padding followed by a '#' character, which may indicate ClickFix or FileFix techniques used to conceal malicious commands from visual inspection.
    ClickFix and FileFix are social engineering attack techniques where adversaries distribute phishing documents or malicious links that deceive users into opening the Windows Run dialog box or File Explorer search bar.
    The victims are then instructed to paste commands from their clipboard, which contain extensive whitespace padding using various Unicode space characters to push the actual malicious command far to the right, effectively hiding it from immediate view.
references:
    - https://expel.com/blog/cache-smuggling-when-a-picture-isnt-a-thousand-words/
    - https://mrd0x.com/filefix-clickfix-alternative/
author: Swachchhanda Shrawan Poudel (Nextron Systems)
date: 2025-11-04
modified: 2025-11-26
tags:
    - attack.execution
    - attack.stealth
    - attack.t1204.004
    - attack.t1027.010
logsource:
    category: process_creation
    product: windows
detection:
    process_creation:
        EventID: 4688
        Channel: Security
    selection_explorer:
        CommandLine|contains: '#'
        ParentProcessName|endswith: \explorer.exe
    selection_space_variation:
        CommandLine|contains:
            -                # En Quad (U+2000)
            -                # Em Quad (U+2001)
            -                # En Space (U+2002)
            -                # Em Space (U+2003)
            -                # Three-Per-Em Space (U+2004)
            -                # Four-Per-Em Space (U+2005)
            -                # Six-Per-Em Space (U+2006)
            -                # Figure Space (U+2007)
            -                # Punctuation Space (U+2008)
            -                # Thin Space (U+2009)
            -                # Hair Space (U+200A)
            -                # No-Break Space (U+00A0)
            - '            ' # Normal space (0x20)
    condition: process_creation and (all of selection_*)
falsepositives:
    - Unknown
level: high
ruletype: Sigma

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