Emotet — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 f31978f7e836f85f…

MALICIOUS

Office (OLE) / .XLSX

104.0 KB Created: 2015-06-05 18:19:34 Authoring application: Microsoft Excel
MD5: a36b1544a966a01cc66a66c7284bb85d SHA-1: e693078c76fab34b4369397e9bd4b8285ee3f71c SHA-256: f31978f7e836f85f4456f43496844efc3f531fca4dbf5fa00bf974c186932a46
262 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File T1059.001 PowerShell

The file contains Excel 4.0 macros, including an Auto_Open function that utilizes dangerous APIs like RUN. The macros reconstruct and reference multiple URLs, indicating a downloader functionality. ClamAV detection further supports this, identifying it as 'Doc.Downloader.EmotetExcel02220-9938626-0'. The reconstructed URLs are the primary indicators of compromise.

Heuristics 6

  • 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 (5 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: Doc.Downloader.EmotetExcel02220-9938626-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Doc.Downloader.EmotetExcel02220-9938626-0
  • 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 http://filecabinet.digitalechoes.co.uk/wp-admin/NC/
    • https://gfnl.org/wp-content/rwdBTLqAfNSYW3L/
    • https://heroicanalytics.com/cgi-bin/SBM4ayPjOSsaclFMKm/
    • https://infosurdesonora.com/css/2RtVpek/
    • https://osklinikken.no/wp-admin/zM2zo0qexb8Ng/

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_macros.txt
be1ac9f30af65ef180310243cbba4a51ea41ae015d1d5e2b649c82e30f6f4b5c		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6365 bytes

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