Malicious Office (OOXML) / .XLSX — malware analysis report

Static analysis result for SHA-256 8f3015ee9e50666a…

MALICIOUS

Office (OOXML) / .XLSX

24.5 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: a0ff3f79f62d3c9ccab854819cad2e26 SHA-1: 714b6a7b26ef951482b5ef6802c7143636f69856 SHA-256: 8f3015ee9e50666a42ee496e1d896b1ed5f7d8684ef450c53ddf90df880ffce9
120 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File T1105 Ingress Tool Transfer

The file is an Excel 4.0 macro sheet, identified by the OOXML_XLM_MACROSHEET heuristic. Critical heuristics indicate the presence of WinAPI and download strings, specifically mentioning URLDownloadToFileA, DownloadToFileA, ShellExecuteA, CreateDirectoryA, URLMon, and Kernel32, along with an .exe path. This strongly suggests the macro's purpose is to download and execute a secondary payload. The macro sheet itself is heavily truncated, preventing a more detailed analysis of the specific download URL or execution path.

Heuristics 2

  • Excel 4.0 macro sheet (1 sheet(s)) critical OOXML_XLM_MACROSHEET
    Spreadsheet contains an Excel 4.0 (XLM) macro sheet — XLM was a major Office malware vector during 2020-2022 and evaded many VBA-focused controls before Microsoft tightened XLM defaults. Even legitimate XLM use is rare in modern workbooks. The macro sheet is stored as XLSB/BIFF12 binary content, which many XML-only OOXML scanners miss.
  • Binary XLM macro sheet with WinAPI/download strings critical OOXML_XLM_BINARY_WINAPI_STRINGS
    Excel 4.0 macro sheet is stored as BIFF12/XLSB binary data and contains Win32 download or process-execution API strings such as URLDownloadToFileA, ShellExecuteA, or CreateDirectoryA. These strings are high-signal in XLM macro sheets and catch payload-download macros that XML-formula scanners cannot parse.

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
99a6a52acb8f5c734f6d86faf89e0637a94ac99f953aa583d2658b47d2e1f9b9		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 194023 bytes

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