Emotet — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 9f4494900e361361…

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: be562628fe311e7f5a23dd83bdd29cf9 SHA-1: 9e4825cc9dcad8b892a872997ded7d46fe65f02e SHA-256: 9f4494900e36136105082af30b1c9cbfe84fba3e30f302c67407dd4b58cac5a4
180 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1059.005 Visual Basic

The sample was detected as Emotet by ClamAV and exhibits characteristics of a downloader. The presence of Excel 4.0 macro sheets within an XLSX file is a strong indicator of malicious intent. The macros are likely responsible for fetching and executing a secondary payload, a common tactic for Emotet.

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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