Office (OOXML) / .XLSX malware analysis — malicious · aa7b7a89879444c9

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 8a1655df75fe7e02d683cbcb5d8ab847 SHA-1: 9b63458977821f5ad6bba463b01d77df8c7c18ba SHA-256: aa7b7a89879444c907f78fdb2905a98904d0412142b21a1931504f0ca6032455

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The file is an Excel spreadsheet containing Excel 4.0 macros, indicated by the OOXML_XLM_MACROSHEET heuristic. These macros are capable of executing arbitrary commands, which is a common technique for initial access or payload delivery. However, the macro content is heavily truncated and obfuscated, preventing a more detailed analysis of its specific actions or the reconstruction of any URLs or commands.

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` `4644d7e1f204a8b7808f5824cc8680185f8a955c9062af91dcd2f831e73ef99b`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	586415 bytes

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