Office (OOXML) / .XLSX malware analysis — malicious · 97fce87ab897d771

MALICIOUS

Office (OOXML) / .XLSX

70.7 KB Created: 2021-03-15 18:27:27 UTC Authoring application: Microsoft Excel 16.0300

MD5: 29420fcb844b31b62a6680d90dc6a830 SHA-1: d87f8772356b41512371c22bb11734070e2fd45e SHA-256: 97fce87ab897d7714e58f7e0b4c1fbf0ccf4100fb6281778f3ff4d7d8d2ea239

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The primary finding is the presence of Excel 4.0 macros within an XLSX file, indicated by the OOXML_XLM_MACROSHEET heuristic. These macros are designed to execute arbitrary commands, which is a common technique for initial access or payload delivery. The script content is heavily obfuscated and truncated, preventing a more detailed analysis of its specific actions or the reconstruction of any URLs or commands. Therefore, the family is unknown and confidence is moderate.

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` `8ca13aa50cfc3b255554b0cbb558251fe26539a51c8fd122c08636bf7b609731`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	95188 bytes

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