Emotet — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 e7065618e785e987…

MALICIOUS

Office (OLE) / .XLSX

118.0 KB Created: 2015-06-05 18:19:34 Authoring application: Microsoft Excel
MD5: 69701651bb9f3fa79939add57b80af9b SHA-1: cd51b80a9bffd89c91958c4b3d8a307b4c96509e SHA-256: e7065618e785e98792d570656fd412ecf695c45ec5a8123d04cf4ee302d225bf
302 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1218.011 Signed Binary Proxy Execution: Rundll32 T1059.005 Command and Scripting Interpreter: Visual Basic

The file contains Excel 4.0 macros, specifically an Auto_Open macro that utilizes dangerous formula APIs. The macro reconstructs and executes 'rundll32.exe' with URLs pointing to external resources. This behavior is consistent with Emotet's typical delivery mechanism, which involves downloading and executing further malicious payloads. The ClamAV detection further supports this attribution.

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 http://www.cuneytkocas.com/wp-content/VSnofpES1wO2CcVob/
    • http://k-antiques.jp/wp-includes/SCYdA6TLohYk2/
    • http://towardsun.net/admin/BYGGkrYAnT/
    • http://www.cuneytkocas.com/wp-content/VSnofpES

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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