Emotet — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 b1184235fe9eea2c…

MALICIOUS

Office (OOXML) / .XLSX

237.9 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-03-11
MD5: 26cc672a9abc4daa8537741972c831f4 SHA-1: 180aac5bed6bc6e00b98c44e7be9b63f1d3a604f SHA-256: b1184235fe9eea2c9193a9ea21ae41fae2c260e84aaafe7d9208054bb4b906ef
180 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1059.005 Visual Basic

The sample is an Excel file containing Excel 4.0 macro sheets, which is a strong indicator of Emotet. The ClamAV detection name 'Xls.Downloader.Emotet-OOXML_XL-af43432fbcb8603c-9980048-0' further supports this attribution. The macros are likely responsible for downloading and executing a second-stage payload, a common Emotet behavior.

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
746c09de869abf9bb2740239d7cc17f7470ed11fe5b974907b1e8d1c3fc94269		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin 2474 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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