Emotet — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 c223b3b52da430ea…

MALICIOUS

Office (OOXML) / .XLSX

233.8 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-03-09
MD5: f75997b5f24a8a6aeb30e280a08e096b SHA-1: bdb9a660df38472f63cbe3b3aec963e5d2b6bffd SHA-256: c223b3b52da430ea8ca61a9c6594a9c814539f1ab7b91aa39c527ce9670be85a
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-af43432fbcb8603c-9980048-0, indicating it is an Emotet downloader. Static analysis revealed the presence of Excel 4.0 macro sheets, which are often used to execute malicious code. The macros are likely responsible for downloading and executing a second-stage 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
ba41a11b1be4eaa156bff86597ea809a971edc4d801f70a4529d6d84b93c19c0		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin 2469 bytes
xlm_sheet_01.bin
294fba96533e16b8e32fcc670b890c44fe9dfc759e5d84743c74026ba7bd4a20		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 428 bytes
xlm_sheet_02.bin
f0daf3cbff097906d4170f35f5f5c2394e9b70d2a487782035c708617ae7b9ec		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet2.bin 428 bytes

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