Office (OOXML) / .XLSX malware analysis — malicious · cd9e2bb272e1f06f

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 137b47d5957763285891caf84b76e884 SHA-1: a3adc46f1a1636926e91fbbdc3807a89b26215db SHA-256: cd9e2bb272e1f06fcf982bd8518c2e034529c42761e39d19a5bdcdf8796512e6

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 an XLSX file. While the macro content is heavily truncated and obfuscated, the presence of this type of macro sheet is a strong indicator of malicious intent, often used to download and execute further stages. The primary IOC is the macro sheet itself.

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` `e2d094ead7aec0bd8d2578c6fc42f0b938e288d39527274955c425cb905720dc`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	7670 bytes

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