Detectionhightest

Uncommon File Created In Office Startup Folder

Detects the creation of a file with an uncommon extension in an Office application startup folder

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Open this Sigma rule in the converter with the YAML preloaded and ready for backend selection.

François Hubaut, Nasreddine Bencherchali (Nextron Systems)Created Sun Jun 05Updated Wed Dec 13a10a2c40-2c4d-49f8-b557-1a946bc55d9dwindows

Log Source

WindowsFile Event

ProductWindows← raw: windows

CategoryFile Event← raw: file_event

Events for file system activity including creation, modification, and deletion.

Detection Logic

detection:
    selection_word_paths:
        - TargetFilename|contains: '\Microsoft\Word\STARTUP'
        - TargetFilename|contains|all:
              - '\Office'
              - '\Program Files'
              - '\STARTUP'
    filter_exclude_word_ext:
        TargetFilename|endswith:
            - '.docb' # Word binary document introduced in Microsoft Office 2007
            - '.docm' # Word macro-enabled document; same as docx, but may contain macros and scripts
            - '.docx' # Word document
            - '.dotm' # Word macro-enabled template; same as dotx, but may contain macros and scripts
            - '.mdb' # MS Access DB
            - '.mdw' # MS Access DB
            - '.pdf' # PDF documents
            - '.wll' # Word add-in
            - '.wwl' # Word add-in
    selection_excel_paths:
        - TargetFilename|contains: '\Microsoft\Excel\XLSTART'
        - TargetFilename|contains|all:
              - '\Office'
              - '\Program Files'
              - '\XLSTART'
    filter_exclude_excel_ext:
        TargetFilename|endswith:
            - '.xll'
            - '.xls'
            - '.xlsm'
            - '.xlsx'
            - '.xlt'
            - '.xltm'
            - '.xlw'
    filter_main_office_click_to_run:
        Image|contains: ':\Program Files\Common Files\Microsoft Shared\ClickToRun\'
        Image|endswith: '\OfficeClickToRun.exe'
    filter_main_office_apps:
        Image|contains:
            - ':\Program Files\Microsoft Office\'
            - ':\Program Files (x86)\Microsoft Office\'
        Image|endswith:
            - '\winword.exe'
            - '\excel.exe'
    condition: ((selection_word_paths and not filter_exclude_word_ext) or (selection_excel_paths and not filter_exclude_excel_ext)) and not 1 of filter_main_*