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

Static analysis result for SHA-256 8c855f9c9fb71bce…

MALICIOUS

Office (OOXML) / .XLSX

80.9 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: d4c05dde40d38fe6c29178295540b636 SHA-1: a34dde59cb1719431b1de25c4dac62c9d97ee1db SHA-256: 8c855f9c9fb71bce2ca09057ba23fc26760f57feeb492119bc4855f5a2e5cd97
60 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic

The critical heuristic firing indicates the presence of Excel 4.0 macros within the XLSX file. While the macro content is truncated, the presence of a path string resembling 'C:\ProgramData\excel.rtf' suggests a potential download or staging location for a secondary payload. This type of macro is commonly used for initial execution and payload delivery.

Heuristics 1

  • 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.

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
7c7b0baba5ccae56fc74a1ec41ec801578e4f8a460f5a722bc82226d7b657483		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 255450 bytes

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