Office (OOXML) / .XLSX malware analysis — malicious · acf90db47063ca44

MALICIOUS

Office (OOXML) / .XLSX

135.6 KB Created: 2021-08-16 09:36:27 UTC Authoring application: Microsoft Excel 12.0000

MD5: c1935e6db0ce006177ead8ca7f3f677e SHA-1: c85b5c25865ac329dfac6bc349c21235ac505b9d SHA-256: acf90db47063ca44a71c7539b2e3e8a902fd7fe7b35e918229a1f327d821353b

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic for Applications

The file is an Excel spreadsheet containing an embedded Excel 4.0 macro sheet, indicated by the OOXML_XLM_MACROSHEET heuristic. While the macro content is truncated and heavily obfuscated, the presence of an XLM macro sheet strongly suggests an attempt to execute arbitrary code upon opening the document. This is a common technique for initial 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.

Filename	Kind	Source	Size
`xlm_sheet_00.bin` `71825c8b08847cdcbe7658f819215f5953a8b47ed038deec18d2a5635563c989`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	619461 bytes

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