Office (OOXML) / .XLSX malware analysis — malicious · 0bcfb0dbe6dda4d6

MALICIOUS

Office (OOXML) / .XLSX

69.2 KB Created: 2021-03-15 18:25:06 UTC Authoring application: Microsoft Excel 16.0300

MD5: 445cf3ad389002cfcb54e07aa3113e2c SHA-1: e619a29897a41983bb8eb5521f314d172c7840f6 SHA-256: 0bcfb0dbe6dda4d624a42608aadb0c060d4216686c968212e9d191fc881a2fc7

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The critical heuristic firing indicates the presence of Excel 4.0 macros within the XLSX file. These macros are known to be used for executing arbitrary commands, often to download and execute further malicious stages. The embedded macro sheet itself is the primary indicator of compromise.

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` `faacbfdcaa1d335ba7161b148b02049406b2858f1a73d6c7bd81aa7a00cab5c9`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	94320 bytes

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