Emotet — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 d73e9e45979ed958…

MALICIOUS

Office (OOXML) / .XLSX

259.9 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-03-03
MD5: 589fc060c91ab7063e8884736330df6c SHA-1: 627237e4532bf85b4a137ed467ef927d320ea6d6 SHA-256: d73e9e45979ed958d35ebf3d9d3c4de6022ba5833604b91fe7e3fceae3e1d085
180 Risk Score

Malware Insights

Emotet · confidence 95%

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

The sample is identified as malicious by ClamAV, specifically as an Emotet downloader utilizing Excel 4.0 macros. The heuristics confirm the presence of multiple XLM macro sheets embedded within an XLSX file. These macros are designed to execute, likely downloading and running a secondary payload, which is characteristic of Emotet's delivery mechanism.

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
0fae9721bd9fbe44a16763b8775a373e32f152386ccea9865e495ec39009be5f		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin 2385 bytes
xlm_sheet_01.bin
5fb96250342084f05e10fa6d990c86431b8f292034e82df9f1af39570894ed28		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 428 bytes
xlm_sheet_02.bin
cbc751d47afd9b56c8d53071fe6c10ee0855a45b530d284e2c7d5d33601799ff		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet2.bin 428 bytes

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