Office (OOXML) / .XLSX malware analysis — malicious · 8c6c5b36589ec9c7

MALICIOUS

Office (OOXML) / .XLSX

98.0 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000 First seen: 2021-11-07

MD5: 3902c34a403020c1ed6507c7f1c547f9 SHA-1: a3969bcecc0ed4d83d76d7249fb05880e03dbba8 SHA-256: 8c6c5b36589ec9c7eb31218709539aa345305e18c1a9bef3837672722d571e62

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 an XLSX file. The embedded script content, though heavily obfuscated and truncated, appears to reference a file path 'C:\ProgramData\excel.rtf', suggesting an attempt to write or execute a file from a common staging location. This points to a macro-based attack pattern aimed at delivering a secondary payload.

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` `e5ba5613cc003a473f794e9af0a1e4d7f71448faa68329eb10690d64328cd24e`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	180531 bytes

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