Emotet — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 3306882403faeb5e…

MALICIOUS

Office (OOXML) / .XLSX

202.4 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300
MD5: 067de2c58a8fb03902b4dbc2fd01e15e SHA-1: b803e6b57b9bf6cb5008ea4688cc2a0135c30d07 SHA-256: 3306882403faeb5e4b0dbb6a7c68e1136f70bdce272aea6a1161128ddaf30819
180 Risk Score

Malware Insights

Emotet · confidence 95%

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

The file is identified as malicious by ClamAV with the signature Xls.Downloader.Emotet-OOXML_XL-af43432fbcb8603c-9980048-0, indicating it is an Emotet downloader. Static analysis revealed the presence of Excel 4.0 macros within an XLSX file, a common delivery mechanism for Emotet. These macros are likely responsible for initiating the download and execution of a secondary malicious payload.

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

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