Emotet — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 89a0cba98818ce66…

MALICIOUS

Office (OOXML) / .XLSX

140.6 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300
MD5: f2735194348be2d55a9f07c5d7dd7825 SHA-1: 41544abb929311e281fe61a4668231654a327670 SHA-256: 89a0cba98818ce66aa9068ecb5dd2494dc7500b6a51009ff39b0dd907da1b738
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. The presence of multiple Excel 4.0 macro sheets within an XLSX file, as indicated by the OOXML_XLM_MACROSHEET and OOXML_XLSB_INTL_MACROSHEET_IN_XLSX heuristics, strongly suggests a downloader. Although the macro content is truncated and obfuscated, the overall structure and ClamAV detection point to Emotet's typical behavior of downloading and executing further stages.

Heuristics 3

  • Excel 4.0 macro sheet (6 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 6

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
0653adaa0192f251911d138528c1dbe3027144fef09ab238ab6e766ab68d7435		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin 2144 bytes
xlm_sheet_01.bin
3a111436a77d4848e01aacfd02e0cce1d8864a62353627d99e8693bdcc6ecda3		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 428 bytes
xlm_sheet_02.bin
70888d71c0f3e07d837486c9995d242cee0ec2c107abf2f3d067ef4eb623c8f6		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet2.bin 428 bytes
xlm_sheet_03.bin
a1c001b0c23ed44acce9385cfa3dae3dab78542f0c5922e35566d00596344c42		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet3.bin 428 bytes
xlm_sheet_04.bin
eeddb8e625b398818efe1da18f363654c09375423eb9196fe0364850d856126f		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet4.bin 477 bytes
xlm_sheet_05.bin
93982a318d983f3133c58897b16da6aef37368f63f0ebfbf2303f95a63f47b92		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet5.bin 428 bytes

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