Office (OOXML) / .XLSX malware analysis — malicious · 325a3238f948846c

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: fcf9790763ac19610740f2cec316dd5f SHA-1: 78f9313a20be0c0cea339ea679008be42fcae346 SHA-256: 325a3238f948846ca535373bcdbdc35913ff1a6d53d0f77568f003f7297da52b

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. The extracted macro content, though truncated, shows a pattern of constructing a file path that resolves to 'C:\ProgramData\excel.rtf'. This suggests the macro's purpose is to write or execute content from this location, likely as a first stage for downloading and running 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` `bc2b1d9178f68df76a19fc9c1c5d2c565df8dd413799b326cd5a869e1526ad76`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	516780 bytes

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