Emotet — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 cb87ccc8388d30e7…

MALICIOUS

Office (OOXML) / .XLSX

234.3 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-03-25
MD5: a1e0a4d231227e9395ca78f99804b63c SHA-1: 623410bf8cfacfffd0396ed18d3c5ef093ac6846 SHA-256: cb87ccc8388d30e7205a563adcd91accb29944adf8fce930821619cab3e69c3e
180 Risk Score

Malware Insights

Emotet · confidence 95%

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

The sample is identified as an Excel 4.0 macro-enabled document, a common delivery mechanism for Emotet. The ClamAV detection explicitly names 'Emotet' and indicates a downloader functionality. The presence of multiple XLM macro sheets strongly suggests the execution of embedded macros, likely to fetch and run a secondary payload.

Heuristics 3

  • Excel 4.0 macro sheet (3 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 3

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
ae4441d805fe3f57aba55504712ba9485a87fe6b13fac9f6a82c3f45d81722b0		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin 2165 bytes
xlm_sheet_01.bin
c20b256a4165081620b14345a8d9f678119919a7e189cc6a97ff5afb49e92fbe		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 428 bytes
xlm_sheet_02.bin
c02ded283c90247f08b3d8fda6ef2762571b1901afb2495531b07c9f34e7fb34		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet2.bin 428 bytes

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