Office (OOXML) / .XLSX malware analysis — malicious · 39d99432698540f5

MALICIOUS

Office (OOXML) / .XLSX

306.8 KB Created: 2021-04-15 15:04:02 UTC Authoring application: Microsoft Excel 16.0300

MD5: 7e00f1f0fabe5bf5404589000e61a9af SHA-1: 9429673fccc8b550a21ea9582c958f8772497b64 SHA-256: 39d99432698540f5ea6b8acf77b2323e2cde143638694bbd726e161924885059

80 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1204.002 Malicious File

The critical heuristic 'OOXML_XLM_MACROSHEET' indicates the presence of Excel 4.0 macros, which are often used for malicious purposes. The external relationship to '2.xlsb' suggests a potential secondary stage or lure. The macrosheet itself is likely responsible for downloading and executing a further payload, though the exact commands are truncated in the provided evidence.

Heuristics 2

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.
External relationship medium OOXML_EXTERNAL_REL

External target in xl/pivotCache/_rels/pivotCacheDefinition1.bin.rels: 2.xlsb

Extracted artifacts 1

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`xlm_sheet_00.bin` `d89ce7f0ee957a82331205e7d02f4dec13b37baf3c9c1191d81862bfe6eb7568`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	1965 bytes

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