Office (OOXML) / .XLSX malware analysis — malicious · d8567a9f7bc749ac

MALICIOUS

Office (OOXML) / .XLSX

62.0 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 16.0300

MD5: 631585c813686625248d1108f84b8519 SHA-1: 221da82bef4d84c8f767f660a1a50b40a40fe166 SHA-256: d8567a9f7bc749ac4eda0741e4192ddae430457441e3b1b5bd40b5c8324d48a3

120 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The sample is an XLSX file containing an embedded Excel 4.0 macro sheet, indicated by the OOXML_XLM_MACROSHEET and OOXML_XLSB_INTL_MACROSHEET_IN_XLSX heuristics. Excel 4.0 macros are capable of executing arbitrary commands, which is a common technique for initial execution and payload delivery. The macro content itself is heavily obfuscated and truncated, preventing a more detailed analysis of its specific actions or any IOCs.

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.
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 1

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`xlm_sheet_00.bin` `c03a19a43999132e3e943a64d9f09c145c1ff1f3e7ec64136db086ccbbd870ca`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin	1811 bytes

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