Emotet — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 4f4f5fca3c53173e…

MALICIOUS

Office (OOXML) / .XLSX

1.07 MB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-04-27
MD5: fb4c282e4bf9d6de200d855d481c3c3e SHA-1: 0f6a1c859c9a9ba0323022e05b79fb032b1d5b24 SHA-256: 4f4f5fca3c53173ede21ef612e55322fc10ab3a16d883295711a6c98cf468f28
200 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File T1105 Ingress Tool Transfer

The critical heuristic 'OOXML_XLM_BINARY_WINAPI_STRINGS' indicates the presence of Excel 4.0 macros that utilize WinAPI functions. The extracted script confirms this, showing the use of 'Kernel32' and 'CreateDirectoryA' functions. Crucially, the script attempts to download a payload from 'sferaoppticall.com/HLlyJ513zu/Cnhfnvmh.png' and 'duddas.com.br/FMPhmkD9g2wZ/Cnhfnvmh.png', likely to execute it. The ClamAV detection explicitly names this as 'Xls.Downloader.Emotet-OOXML_XL'.

Heuristics 4

  • Excel 4.0 macro sheet (1 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.
  • Binary XLM macro sheet with WinAPI/download strings critical OOXML_XLM_BINARY_WINAPI_STRINGS
    Excel 4.0 macro sheet is stored as BIFF12/XLSB binary data and contains Win32 download or process-execution API strings such as URLDownloadToFileA, ShellExecuteA, or CreateDirectoryA. These strings are high-signal in XLM macro sheets and catch payload-download macros that XML-formula scanners cannot parse.
  • 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 4

Files carved from inside the sample during analysis.

FilenameKindSourceSize
ooxml_oleobject_00.bin
40c119c61b868c791f8026a508e33e63ca4fac0d7a1c4dc7423000974f221b99		 ooxml-ole-object OOXML embedded OLE part: xl/embeddings/oleObject8.bin 2743296 bytes
ooxml_oleobject_00_ole10native_00.bin
7a7c5913ea54c058e6c966932426a757075833c57d5321b3033161e975cf6aa8		 ole-package OOXML xl/embeddings/oleObject8.bin Ole10Native stream: Ole10Native 2719588 bytes
emf_00.emf
7d56c82264dc501cee3b2f361127c7160d34aa3a6be5f44017eade57c559b1d1		 ooxml-emf OOXML EMF part: xl/media/image2.emf 5439552 bytes
xlm_sheet_00.bin
60b295ec520cfeea8dabac7bd1a846c8211853edb956cb11145b0ff1b24cc0a3		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 2954 bytes

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