Office (OOXML) / .XLSX malware analysis — malicious · a484ce1a1ed13cfe

MALICIOUS

Office (OOXML) / .XLSX

239.0 KB Created: 2021-08-16 09:36:27 UTC Authoring application: Microsoft Excel 12.0000

MD5: 8f61479cf0003dd2af9bdc1ca1d09791 SHA-1: 1ee568a321f9ee682602f064524065d7c8f955c4 SHA-256: a484ce1a1ed13cfee6d1ffe86397f5241bde9d781dc25e7347bde0f5f42c85ba

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 capable of executing arbitrary commands, which is a common technique for initial access or payload delivery. However, the macro content itself is heavily truncated and obfuscated, preventing a detailed analysis of its specific actions or the reconstruction of any URLs or commands.

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` `27ab23c0bc4f92739ca99b0e00b7f853d9ac8337c2c0b31400f8be3a6044afac`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	373965 bytes

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