Suspicious Explorer Process with Whitespace Padding - ClickFix/FileFix

calendar Nov 27, 2025 · attack.execution attack.t1204.004 attack.defense-evasion attack.t1027.010  ·
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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.

Sigma rule (View on GitHub)

 1title: Suspicious Explorer Process with Whitespace Padding - ClickFix/FileFix
 2id: 3ae9974a-eb09-4044-8e70-8980a50c12c8
 3related:
 4    - id: 8f2a5c3d-9e4b-4a7c-8d1f-2e5a6b9c3d7e
 5      type: similar
 6    - id: 7a1b4c5e-8f3d-4b9a-7c2e-1f4a5b8c6d9e
 7      type: similar
 8status: experimental
 9description: |
10    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.
11    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.
12    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.    
13references:
14    - https://expel.com/blog/cache-smuggling-when-a-picture-isnt-a-thousand-words/
15    - https://mrd0x.com/filefix-clickfix-alternative/
16author: Swachchhanda Shrawan Poudel (Nextron Systems)
17date: 2025-11-04
18modified: 2025-11-26
19tags:
20    - attack.execution
21    - attack.t1204.004
22    - attack.defense-evasion
23    - attack.t1027.010
24logsource:
25    category: process_creation
26    product: windows
27detection:
28    selection_explorer:
29        ParentImage|endswith: '\explorer.exe'
30        CommandLine|contains: '#'
31    selection_space_variation:
32        CommandLine|contains:
33            - '            ' # En Quad (U+2000)
34            - '            ' # Em Quad (U+2001)
35            - '            ' # En Space (U+2002)
36            - '            ' # Em Space (U+2003)
37            - '            ' # Three-Per-Em Space (U+2004)
38            - '            ' # Four-Per-Em Space (U+2005)
39            - '            ' # Six-Per-Em Space (U+2006)
40            - '            ' # Figure Space (U+2007)
41            - '            ' # Punctuation Space (U+2008)
42            - '            ' # Thin Space (U+2009)
43            - '            ' # Hair Space (U+200A)
44            - '            ' # No-Break Space (U+00A0)
45            - '            ' # Normal space (0x20)
46    condition: all of selection_*
47falsepositives:
48    - Unknown
49level: high

References

  • Cache smuggling: When a picture isn’t a thousand words

    We recently observed an innovative campaign using the ClickFix attack tactic for cache smuggling. Here's what you need to know.


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  • Presenting an alternate method to the traditional ClickFix attack. Introduction Over the past few weeks, I’ve been working on the upcoming update for the Offensive Phishing Operations Course. The u...


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