Office (OOXML) / .XLSX malware analysis — malicious · 28b92e3c6034fa90

MALICIOUS

Office (OOXML) / .XLSX

79.1 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000

MD5: 00fd3bcb0037cee8e3ebab152962cb19 SHA-1: 918ca66efeb426e3eb7763861776f96466406afd SHA-256: 28b92e3c6034fa90e3e42bb2b400d57af01d62819349a29ea176c531059489c0

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The sample is an Excel file identified as containing Excel 4.0 macros. The heuristic firing indicates the presence of these macros, which are often used to execute arbitrary commands or download additional payloads. The macro 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 exact attack pattern and family remain uncertain.

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` `2c49340e71c96e550427e23aa565b7d4d98d24208637f91e145ede62cc1480f5`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	7497 bytes

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