Detectionhighstable

Suspicious Double Extension File Execution

Detects suspicious use of an .exe extension after a non-executable file extension like .pdf.exe, a set of spaces or underlines to cloak the executable file in spear phishing campaigns

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Launch

Florian Roth (Nextron Systems), @blu3_team, Nasreddine Bencherchali (Nextron Systems)Created Wed Jun 26Updated Fri May 301cdd9a09-06c9-4769-99ff-626e2b3991b8windows

Log Source

WindowsProcess Creation

ProductWindows← raw: windows

CategoryProcess Creation← raw: process_creation

Events generated when a new process is spawned on the system. Covers command-line arguments, parent/child relationships, and process metadata.

Detection Logic

detection:
    selection:
        Image|endswith:
            - '      .exe'
            - '______.exe'
            - '.doc.exe'
            - '.doc.js'
            - '.docx.exe'
            - '.docx.js'
            - '.gif.exe'
            - '.jpeg.exe'
            - '.jpg.exe'
            - '.mkv.exe'
            - '.mov.exe'
            - '.mp3.exe'
            - '.mp4.exe'
            - '.pdf.exe'
            - '.pdf.js'
            - '.png.exe'
            - '.ppt.exe'
            - '.ppt.js'
            - '.pptx.exe'
            - '.pptx.js'
            - '.rtf.exe'
            - '.rtf.js'
            - '.svg.exe'
            - '.txt.exe'
            - '.txt.js'
            - '.xls.exe'
            - '.xls.js'
            - '.xlsx.exe'
            - '.xlsx.js'
            - '⠀⠀⠀⠀⠀⠀.exe' # Unicode Space Character: Braille Pattern Blank (Unicode: U+2800)
        CommandLine|contains:
            - '      .exe'
            - '______.exe'
            - '.doc.exe'
            - '.doc.js'
            - '.docx.exe'
            - '.docx.js'
            - '.gif.exe'
            - '.jpeg.exe'
            - '.jpg.exe'
            - '.mkv.exe'
            - '.mov.exe'
            - '.mp3.exe'
            - '.mp4.exe'
            - '.pdf.exe'
            - '.pdf.js'
            - '.png.exe'
            - '.ppt.exe'
            - '.ppt.js'
            - '.pptx.exe'
            - '.pptx.js'
            - '.rtf.exe'
            - '.rtf.js'
            - '.svg.exe'
            - '.txt.exe'
            - '.txt.js'
            - '.xls.exe'
            - '.xls.js'
            - '.xlsx.exe'
            - '.xlsx.js'
            - '⠀⠀⠀⠀⠀⠀.exe' # Unicode Space Character: Braille Pattern Blank (Unicode: U+2800)
    condition: selection