Office (OOXML) / .XLSX malware analysis — malicious · 75798031500c5903

MALICIOUS

Office (OOXML) / .XLSX

120.4 KB Created: 2021-03-29 19:56:22 UTC Authoring application: Microsoft Excel 16.0300

MD5: ffdd461c52a57102740b3ccfec9a4b5b SHA-1: 9c5c775fc06b65b86c314dfad1ee9da24824e785 SHA-256: 75798031500c5903fb5b84db6bcb1347c361b799640be2734189cdc7ffa3dcb2

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1566.001 Spearphishing Attachment

The file is an Excel spreadsheet containing Excel 4.0 macros, identified by the OOXML_XLM_MACROSHEET heuristic. These macros are likely designed to download and execute a secondary payload, a common technique for initial access via spearphishing attachments. The specific macro content was truncated, preventing a more detailed analysis of the payload's behavior or specific IOCs.

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` `e05302ce92e08a9d683ac88470fac689a82880a9a4f8b0ab1a63e7391157ba33`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	91649 bytes

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