Office (OOXML) / .XLSX malware analysis — malicious · 8b28f9624a96597f

MALICIOUS

Office (OOXML) / .XLSX

83.7 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000

MD5: 6f0d7c1052a02debbabdb46057a26767 SHA-1: 10ee9a28ef0aaecf138709c350366daa4b61551c SHA-256: 8b28f9624a96597fe1c164ddbb843f0fbc262744efc8154649c31251a71ef1a5

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The critical heuristic firing indicates the presence of an Excel 4.0 macro sheet. The macro sheet contains obfuscated strings that reconstruct to a file path, 'C:\ProgramData\excel.rtf'. This suggests the macro is intended to write or execute a file from this location, likely as part of a multi-stage attack. The exact execution flow is unclear due to truncation, but the pattern is consistent with macro-based malware 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.

Filename	Kind	Source	Size
`xlm_sheet_00.bin` `6cb5ff6ce3f1787933e170cb4919a47efbee3417702a8070ea6924be7278f6a4`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	126491 bytes

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