Emotet — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 f9ac16f1e70bc00b…

MALICIOUS

Office (OOXML) / .XLSX

202.4 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300
MD5: ffa95ac26838fd8f26dec613343173a2 SHA-1: fc4c129126311fc7d3bd6175e541c72e3b6bd22f SHA-256: f9ac16f1e70bc00b1a6fe9adcd8bc1e36c2dcd143b1003f65d8bd39487bdf8c0
180 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File

The file is identified as a malicious Excel 4.0 macro sheet, specifically flagged as Emotet. The presence of XLM macros indicates an attempt to execute code directly from the spreadsheet. The ClamAV detection name further supports the Emotet family attribution and suggests a downloader functionality. This points to an attack pattern where the macro is used to fetch and run additional malicious content.

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
a2d4f9910b57a5ea9f0f60a8236ec6d4a482a9e70e10e8d1d85ef6205b8ccd09
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin 1799 bytes