Office (OOXML) / .XLSX malware analysis — malicious · fdbe8c7bc44589f6

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: e69a4e02eb8a57ae5ec8d614b75fe93e SHA-1: 25e7ea9d8e0915661851c1e1b70e3761d233cf6a SHA-256: fdbe8c7bc44589f665fa238212e45a94caba79424e37abd7499636cc1e05ecf6

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The critical heuristic firing indicates the presence of Excel 4.0 macros. While the macro content is heavily obfuscated and truncated, the presence of a path string resembling 'C:\ProgramData\excel.rtf' suggests a potential download or staging location for a second-stage payload. This type of macro is commonly used for initial access and payload delivery.

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` `d619f47eb9c8ef55235ece8212fbf363e5447e0962d67b0348d1377d0523b750`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	159263 bytes

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