Emotet — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 c0e91f1caa569816…

MALICIOUS

Office (OLE) / .XLSX

118.0 KB Created: 2015-06-05 18:19:34 Authoring application: Microsoft Excel
MD5: e37f1632461e0a2ffea36228f94687ec SHA-1: 3dd67b23a10d023a531e3754ad65d246f65d6d99 SHA-256: c0e91f1caa569816aac5c6dc3fc878ebf80cd72d580e18e1bdafa0835d9504fe
302 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1059.005 Visual Basic T1218.011 Rundll32 T1071.001 Web Protocols

The file contains Excel 4.0 macros with an Auto_Open entry, a known technique for executing malicious code. The macros reconstruct and execute 'rundll32.exe' with URLs pointing to malicious payloads. ClamAV detection further confirms its malicious nature, identifying it as an Emotet downloader.

Heuristics 7

  • Excel 4.0 Auto_Open defined name critical OLE_XLM_AUTOOPEN_DEFINEDNAME
    oletools recovered an Auto_Open / Auto_Close entry from an Excel 4.0 macro sheet. The raw BIFF name can be tokenized or partially opaque to byte-string checks, but the recovered macro listing confirms the workbook has an XLM auto-execution entry.
  • XLM Auto_Open with dangerous formula APIs critical OLE_XLM_DANGEROUS_FN
    Excel 4.0 macro sheet contains an Auto_Open / Auto_Close entry and dangerous XLM formula APIs that can invoke programs, write files, or transfer control without VBA.
  • URL reconstructed from XLM cell array (3 URLs) critical OLE_XLM_CELL_ARRAY_URL
    Excel 4.0 macro sheet stages its payload URL across the BIFF8 Shared String Table (one quoted-char SST entry concatenated with & at runtime) or across individual numeric cells (one ASCII charcode per cell). The reconstructed URL is invisible to literal-bytes URL extraction because it is never contiguous in the workbook stream. URLs were recovered by walking the BIFF8 record stream and decoding SST entries plus LABELSST/RK/NUMBER cells.
  • ClamAV: Xls.Downloader.Emotet-bd646319c2d29cd6-9951195-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.Emotet-bd646319c2d29cd6-9951195-0
  • LOLBin token sequence in document text high SE_LOLBIN_RUN_COMMAND
    Extracted document text contains a Windows script/execution tool name (PowerShell, mshta, cmd, rundll32, regsvr32, …) within 220 characters of a dangerous flag, command verb, or URL. This is a visible 'run this' instruction in HTML/PDF/RTF lure bodies, or — in macro-laden Office files — the macro's own string-pool entries appearing adjacent in extracted text.
  • Excel 4.0 (XLM) macro sheet present medium OLE_XLM_AUTOOPEN
    Workbook contains an Excel 4.0 macro sheet sub-stream — XLM is rarely seen in modern legitimate workbooks and was a major Office malware vector during 2020-2022.
  • Embedded URL info EMBEDDED_URL
    One or more URLs were extracted from the document. The URL itself is not a detection — see the per-URL labels for which channel (macro, JS, link annotation, document body, ...) reached each URL.
    URL https://wordpressdes.vanzolini-gte.org.br/fundacaotelefonica.org.br/gAbC4QpJYI/
    • http://txingame.com/wp-content/PwKfVQfdhHbAv2j/
    • http://shopnhap.com/highbinder/nnYko9FDNJ/
    • https://wordpressdes.vanzolini-gte.org.br/fund

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_macros.txt
4d32d4bc18234076b76fff05a9ee50b43b756f16fa43d7a1a9cb0b5c555b4ddf		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 4504 bytes

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