Office (OOXML) / .XLSX malware analysis — malicious · 99bdf26a2b704ac0

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: cb3874cfc9d1edeb86c2d3b14856a4ee SHA-1: b26e7a014159d608c4c006dd20fde3c2ac2a1597 SHA-256: 99bdf26a2b704ac057a01d67854f08654dccec1145c784793d2a2a19f19bb3a0

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. The macro sheet content is heavily obfuscated and truncated, preventing a detailed analysis of its specific actions. However, the presence of Excel 4.0 macros strongly suggests an attempt to execute arbitrary code, likely for malicious purposes such as downloading a secondary 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` `f2f8dbc6f7673d154554079adfb17897005e325844a3bb8235ac16c811473b38`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	428713 bytes

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