Office (OOXML) / .XLSX malware analysis — malicious · 2281687f22fcb5f1

MALICIOUS

Office (OOXML) / .XLSX

1.16 MB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-04-08

MD5: 6776769a08f3e1c58a8e90fe167a76fa SHA-1: c5ac470bfaf9cc4621f3149215a9e4d75a08fe05 SHA-256: 2281687f22fcb5f1cbf39a5cfa2ee3b9e6bbc04eccddaf6907f23ce456e2618e

120 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The file is an XLSX document containing multiple Excel 4.0 macro sheets. These macros are known to be used for arbitrary code execution, often to download and run further malicious content. While the specific macro commands are heavily obfuscated and truncated in the provided excerpts, the presence of these macro sheets strongly indicates a malicious intent. No specific family could be identified, and no direct IOCs like URLs or hashes were extracted from the macro content.

Heuristics 2

Excel 4.0 macro sheet (4 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.
XLSB international XLM macro sheet hidden in .xlsx critical OOXML_XLSB_INTL_MACROSHEET_IN_XLSX

OOXML package is named .xlsx but contains XLSB workbook parts and an international Excel 4.0 macro sheet. This hides XLM macro execution from scanners that trust the extension or only inspect XML worksheet parts. The technique is macro execution, not a document-parser CVE.

Extracted artifacts 5

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`emf_00.emf` `36bcdb650f3335661fd30903e4ddbb92ac947513ed380f203fccc03424ff9fe4`	ooxml-emf	OOXML EMF part: xl/media/image1.emf	6145428 bytes
`xlm_sheet_00.bin` `44e1c910560c290cf1fe3eb0d0256a21f957a1765ea926de110b1985b1f72819`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin	1717 bytes
`xlm_sheet_01.bin` `ec25b05dca7aaeaed79bb62fb6411ee9f85904d5e8709aa43d05d83ea361677c`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet2.bin	792 bytes
`xlm_sheet_02.bin` `f0a9425b8507f47d4bffbfc9986e6f77a1eec5a7b094745fec3307154c314949`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	402 bytes
`xlm_sheet_03.bin` `7b780847888f3179b9a2306b1d9dd4b22d991fb4b1641b18d3184a5b6ac9038f`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet2.bin	322 bytes

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