Office (OOXML) / .XLSX malware analysis — malicious · bfdfd4c65d282dad

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 72965a4c8edbd0576942730a4e1c8f48 SHA-1: c5691fd8de0eb3ee9523521b4ec04499e2a2e0e3 SHA-256: bfdfd4c65d282dad4fa052d1babc1e4f9841bbca81e849a1aa865956e338fbae

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 such macros strongly suggests an intent to download and execute a secondary payload, a common technique for initial access. The specific macro sheet filename is included as an IOC.

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` `453afe58a17d9b4a8e32a2e2752633efb83ba98002720f612dd6a23735b4aedb`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	3918 bytes

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