Office (OOXML) / .XLSX malware analysis — malicious · ff8a5448a444ce37

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: cb0cdc631061a6134c108fb54191f29d SHA-1: 94e1c01dfc6eefb029785fde482ec5d94809881f SHA-256: ff8a5448a444ce375ebe0d59562fe68d9c952d032be852a29d830eb2721627f9

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The critical heuristic firing indicates the presence of Excel 4.0 macros. These macros appear to be constructing a file path, likely for dropping a payload, to 'C:\ProgramData\excel.rtf'. The exact function of the dropped file is not clear from the available script data, but the file path construction is a strong indicator of malicious intent.

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` `747b367a237197a80558f8f1e497d7efadccad5c79a6c26dd0e612026b0ed519`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	593852 bytes

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