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

Static analysis result for SHA-256 be5a8f70ae8ccfcb…

MALICIOUS

Office (OOXML) / .XLSX

26.4 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: 5eb30099f2f93224c17fa830b5ec766a SHA-1: d2780d4f049232eb96c5608afe6b010446766fe9 SHA-256: be5a8f70ae8ccfcb1dbb5bb0e7d8b24f3a8d5fa74b8e7184610dc8f449846974
182 Risk Score

Malware Insights

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

The file contains Excel 4.0 macros, which are known to be used for malicious purposes. The macros contain strings indicative of WinAPI calls such as URLDownloadToFileA and ShellExecuteA, suggesting the intent to download and execute a second-stage payload. The reconstructed URL from the macro is https://revistascientificas.posgradocolumbia.edu.py/ds/3.gif, which is likely the source of the payload.

Heuristics 4

  • 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.
  • URL reconstructed from XLM cell array (1 URL) critical OOXML_XLM_CELL_ARRAY_URL
    Excel 4.0 macro sheet stages its payload URL across individual numeric cells (one ASCII charcode per cell) or inside an embedded HTA that uses VBScript Chr()/&-concat obfuscation. The reconstructed URL is invisible to literal-bytes URL extraction because it is never contiguous in the workbook stream. URLs were recovered by walking the BIFF12 record stream of every worksheet and macrosheet part and decoding RK/inline-string cells in both row-major and column-major order.
  • Embedded URL info EMBEDDED_URL
    One or more URLs were extracted from the document. The URL itself is not a detection — see the per-URL labels for which channel (macro, JS, link annotation, document body, ...) reached each URL.
    URL https://revistascientificas.posgradocolumbia.edu.py/ds/3.gif

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
4be47f6fcaf3ddcd2c09a8b9ee903affb3f4991b54c12b0197126fd22afb2207		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 200547 bytes

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