Emotet — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 8fc355ade40cae7c…

MALICIOUS

Office (OOXML) / .XLSX

1.01 MB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-04-13
MD5: c15611e7c5ec4889bebd60ce73f2126a SHA-1: 445549a8d5a7828cd98b22fcbbcf6fcead30b5ef SHA-256: 8fc355ade40cae7c4a47264b44a5d8204a574a2dffb7dee74e9007fce0f87802
200 Risk Score

Malware Insights

Emotet · confidence 95%

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

The critical heuristic 'OOXML_XLM_MACROSHEET' indicates the presence of Excel 4.0 macro sheets, which are often used for malicious purposes. ClamAV detection confirms this, identifying the file as 'Xls.Downloader.Emotet-OOXML_XL-af43432fbcb8603c-9980048-0'. The embedded OLE object and the nature of the macro sheets suggest a downloader functionality, likely to fetch and execute further malicious content.

Heuristics 4

  • Excel 4.0 macro sheet (4 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
  • Embedded OLE object medium OOXML_OLE_OBJECT
    Document contains an embedded OLE object

Extracted artifacts 7

Files carved from inside the sample during analysis.

FilenameKindSourceSize
ooxml_oleobject_00.bin
93b1cea548cf9d5f4ac6f64afb7be18c1737b3dbdea4bd0aadb26bf7b8d79518		 ooxml-ole-object OOXML embedded OLE part: xl/embeddings/oleObject2.bin 3099136 bytes
ooxml_oleobject_00_ole10native_00.bin
a6724425b761391a2288cdb0e402bdc8cf2de9a4e93260c95af92b78344a367e		 ole-package OOXML xl/embeddings/oleObject2.bin Ole10Native stream: Ole10Native 3072068 bytes
emf_00.emf
3f0f6bb70f3d65dcc8d248d78ac320bcc22b1148ea5fdd2c1043065d03460133		 ooxml-emf OOXML EMF part: xl/media/image1.emf 6144552 bytes
xlm_sheet_00.bin
c2021f3cd7a15d00132d83f817974fbaa3dcba6ac2832cfc59e171f9725dd194		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin 1816 bytes
xlm_sheet_01.bin
2e5c804d6e95dfaf0aedb09d41e9590a894531b97c42c90478ac456e59a2157a		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet2.bin 832 bytes
xlm_sheet_02.bin
f0a9425b8507f47d4bffbfc9986e6f77a1eec5a7b094745fec3307154c314949		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 402 bytes
xlm_sheet_03.bin
7b780847888f3179b9a2306b1d9dd4b22d991fb4b1641b18d3184a5b6ac9038f		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet2.bin 322 bytes

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