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

Static analysis result for SHA-256 3cb29957c522c75d…

MALICIOUS

Office (OOXML) / .XLSX

26.3 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: 7307bb3bcd8c6397bb54b79f06f73fc6 SHA-1: e52013d30c1e0658ba229ac7c1f1f9df78c60070 SHA-256: 3cb29957c522c75d6c07ebfdfcd85035143f64b025b558cf15e4684fe404c290
182 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Service Execution: Service Execution T1204.002 Malicious File: Malicious File T1105 Ingress Tool Transfer

The file contains Excel 4.0 macros, which are known to be used for malicious purposes. The macros utilize WinAPI functions such as URLDownloadToFileA and ShellExecuteA to download and execute a second-stage payload from the URL https://absolutefitnessgym.com/ds/3.gif. The presence of these functions and the embedded URL strongly suggest a downloader attack pattern.

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://absolutefitnessgym.com/ds/3.gif

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
33b39070cf703fb8920ce299136e91bbc3d2e0dae01e819c4b64ba4e4c896109		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 200463 bytes

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