Emotet — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 76bac667effce42b…

MALICIOUS

Office (OOXML) / .XLSX

135.6 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300
MD5: f6fb7a8f6c2c5f45385d93bf489296b2 SHA-1: adc7dda7e8add9c015629810aabf6eaf970ce7d7 SHA-256: 76bac667effce42b08ca228acbeb9d3c4671c3e53c8cbb8df99d415037b2bc55
180 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1059.005 Visual Basic

The file is identified as malicious by ClamAV, specifically as an Emotet downloader. Static analysis reveals the presence of Excel 4.0 macros within an XLSX file, a common delivery method for Emotet. The macros are likely responsible for downloading and executing a secondary payload, which is characteristic of Emotet's infection chain.

Heuristics 3

  • 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.
  • XLSB international XLM macro sheet hidden in .xlsx critical OOXML_XLSB_INTL_MACROSHEET_IN_XLSX
    OOXML package is named .xlsx but contains XLSB workbook parts and an international Excel 4.0 macro sheet. This hides XLM macro execution from scanners that trust the extension or only inspect XML worksheet parts. The technique is macro execution, not a document-parser CVE.
  • ClamAV: Xls.Downloader.Emotet-OOXML_XL-af43432fbcb8603c-9980048-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.Emotet-OOXML_XL-af43432fbcb8603c-9980048-0

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
503cc5255e3893c37771adee7e13daba46e5b4071e56a514ef4cc61cc6d637cd		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin 1769 bytes

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