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

Static analysis result for SHA-256 e7664cc17d8ec361…

MALICIOUS

Office (OOXML) / .XLSX

26.3 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: 66e4220503722028dbb42b6960274f8b SHA-1: 7501c5f80747a6131db77909949bbaa399e7466e SHA-256: e7664cc17d8ec3611b84a49b4475ffa7d6f57e52ce1a850145c0747890d37675
182 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. It contains WinAPI strings related to downloading and executing files, such as URLDownloadToFileA and ShellExecuteA. The macro reconstructs a URL, https://columbia25.aula-web.net/ds/3.gif, which is likely used to download a second-stage payload. The presence of these WinAPI calls and the reconstructed URL strongly indicate a downloader functionality.

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://columbia25.aula-web.net/ds/3.gif

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
6651bdb46904db7afdc3e5576514edde72d47967bab1a40096ef116c3930aae0		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 200467 bytes

Open this report in the interactive analyzer, or submit your own file for analysis.