Emotet — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 1c933e0e700ec321…

MALICIOUS

Office (OOXML) / .XLSX

265.1 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-02-23
MD5: b1bbbea9ac6472925d3fa03502b46186 SHA-1: c25bdfb4f4b33c3326eaad4f3f3da4154f157e33 SHA-256: 1c933e0e700ec3213076a40d08e32195c2d1cb3fed623d6907010e4f069e9cd0
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 as 'Xls.Downloader.Emotet-OOXML_XL-af43432fbcb8603c-9980048-0'. Static analysis revealed the presence of Excel 4.0 macros within an XLSX file, a known technique for delivering Emotet. The embedded macro sheet is heavily obfuscated, but the heuristic firings strongly indicate its role as a downloader for a second-stage 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
0739caeaa979fb9b94d312f443a973e7c53ed4452081346db704e2fcaccfba81		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin 1768 bytes

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