Office (OOXML) / .XLSX malware analysis — malicious · 146a181a98bd1db7

MALICIOUS

Office (OOXML) / .XLSX

88.5 KB Created: 2021-03-15 18:25:26 UTC Authoring application: Microsoft Excel 16.0300

MD5: 2b484732645be215cdd1e6df3e0b3658 SHA-1: 662c0e933c46bd7d5890d2d2242822d5cfb97085 SHA-256: 146a181a98bd1db7904f2856847fd4b204fd0ee71e75e60552ad9c4baab02e38

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. While the macro content is heavily obfuscated and truncated, the presence of XLM macros strongly suggests an attempt to execute arbitrary code, likely to download and run a second-stage payload. The specific functionality cannot be determined with high confidence due to the obfuscation.

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` `28d3cbda6ed8fa49159b6e145a5e844b5418c02771e57524abd1b62ac4c06e1d`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	97804 bytes

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