Office (OOXML) / .XLSX malware analysis — malicious · c0be2b35778de9b2

MALICIOUS

Office (OOXML) / .XLSX

102.4 KB Created: 2021-02-03 15:28:44 UTC Authoring application: Microsoft Excel 16.0300

MD5: 4567910e5ab113f08eb7edd48152074b SHA-1: af5213aa157cc35875778cdf85bb70673b66e53b SHA-256: c0be2b35778de9b2feb0740482b838b4b774e6870cf12f18799624b54cdf97f0

120 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The file is an Excel spreadsheet containing disguised Excel 4.0 macros, indicated by the OOXML_XLM_MACROSHEET and OOXML_XLM_DISGUISED_RELATIONSHIP heuristics. The macros are heavily obfuscated and truncated, preventing a detailed analysis of their specific actions. However, the presence of disguised macros strongly suggests an attempt to download and execute a secondary payload.

Heuristics 2

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.
Excel 4.0 macro sheet stored under disguised package path critical OOXML_XLM_DISGUISED_RELATIONSHIP

OOXML package declares an xlMacrosheet relationship whose target is outside the canonical xl/macrosheets/ path. Excel follows the relationship type, while path-only scanners can miss the macro execution surface.

Extracted artifacts 1

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`xlm_sheet_00.bin` `94707f6392390fbf645232ea532d200479c173acb4209f458ddb3908ebb95b19`	xlm-macrosheet	OOXML XLM macro sheet: xl/de/sheet1.bin	1007414 bytes

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