Emotet — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 306433cdeddadf92…

MALICIOUS

Office (OOXML) / .XLSX

257.9 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-02-16
MD5: 05f034563d28cfcb02445fc33f0da4be SHA-1: 8ab93f526e5e896e0aa6b250c538ac35e3feaa0c SHA-256: 306433cdeddadf922a7849ab12431fbdb1f1f7f23dc4de1c2e378dcf9a05ca8a
180 Risk Score

Malware Insights

Emotet · confidence 95%

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

The file is an Excel XLSX containing embedded Excel 4.0 macro sheets, as indicated by the OOXML_XLM_MACROSHEET and OOXML_XLSB_INTL_MACROSHEET_IN_XLSX heuristics. The ClamAV detection explicitly names this as 'Xls.Downloader.Emotet-OOXML_XL'. The macro sheets themselves are heavily obfuscated but their presence and the detection strongly suggest a downloader functionality, likely for Emotet malware. The primary attack pattern involves leveraging these macros to execute a malicious 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
7882e9bc1af9baf322c46fdf40ee697d3478a5e1340250d547de82a512dbe59b		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin 2439 bytes
xlm_sheet_01.bin
86382bd657c1c4063683e9cb42624589f8aa1fc621f270bbb5041fb8508b304b		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 484 bytes
xlm_sheet_02.bin
0a9fa880b5a7546c7b56783abe7e1c4298c1e8624103cd161e3dac9c5603a3f0		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet2.bin 484 bytes

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