Office (OOXML) / .XLSX malware analysis — malicious · b4d5d8727bd02cd0

MALICIOUS

Office (OOXML) / .XLSX

152.0 KB Created: 2021-10-04 08:20:54 UTC Authoring application: Microsoft Excel 12.0000

MD5: b3513e24471feef7d01f4e74fbfaea76 SHA-1: d3e5d3d9cf5854e217f40d2ea329d99b270aa77c SHA-256: b4d5d8727bd02cd0506998202159e38b61e0351e989a717dc30e63f3d66f0e50

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The sample is an Excel file containing Excel 4.0 macros, indicated by the OOXML_XLM_MACROSHEET heuristic. While the macro content is heavily truncated and obfuscated, the presence of Excel 4.0 macros strongly suggests an attempt to execute arbitrary code. This is a common technique for initial access or downloading and executing a second-stage payload.

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` `b5b5c30acca727a76f0baaec3744b96ecf3467c6ac15e364c57bcd757c6246ab`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	384449 bytes

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