Office (OOXML) / .XLSX malware analysis — malicious · 25c3b793439f12d9

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: d8251372d563adc146f9a79720c03a7b SHA-1: a048d146a5ea68985f35560e5f8e9da6cc329e2b SHA-256: 25c3b793439f12d9240fb9d1d09dfed0122c74e3370d08d98a45a6302ba2906c

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. This is a common method for initial execution, often leading to the download and execution of further malicious content. The macro sheet itself is listed 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` `014d3697380c499179889fe74ee9e94408defcda520b2997be1654749d4042e5`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	260566 bytes

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