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

Static analysis result for SHA-256 2d659e7701fdd879…

MALICIOUS

Office (OOXML) / .XLSX

154.0 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 16.0300
MD5: 008e2b469abf7058701ed9809ba1f949 SHA-1: d3c7adb371859497a0e3b61796a9469b1e9d1721 SHA-256: 2d659e7701fdd879c933ca2f625d7183810342fd79a75d476dd68f4c3b8eeeb4
120 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic

The file is an XLSX document containing multiple Excel 4.0 macro sheets, identified by the OOXML_XLM_MACROSHEET and OOXML_XLSB_INTL_MACROSHEET_IN_XLSX heuristics. While the exact commands within the truncated macro sheets are not fully discernible, the presence and nature of these macros strongly suggest an intent to execute arbitrary code, typically for downloading and executing further malicious content. The confidence is moderate due to the truncated nature of the script content.

Heuristics 2

  • Excel 4.0 macro sheet (3 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.
  • XLSB international XLM macro sheet hidden in .xlsx critical OOXML_XLSB_INTL_MACROSHEET_IN_XLSX
    OOXML package is named .xlsx but contains XLSB workbook parts and an international Excel 4.0 macro sheet. This hides XLM macro execution from scanners that trust the extension or only inspect XML worksheet parts. The technique is macro execution, not a document-parser CVE.

Extracted artifacts 3

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
9a232684b90b1697660b058dac0594697a629fc26ba9e0c572e4e8b3c6d09add		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin 5899 bytes
xlm_sheet_01.bin
86d47db54f15ba79e074bf90a680ee1fab1f3289b1916ec55a3001da53ffb657		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet2.bin 1158 bytes
xlm_sheet_02.bin
6e9f760f0197fd4535c8f2ecca590c8bedd4b8505085915e283f4133345daa26		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet3.bin 6203 bytes

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