Emotet — Office (OLE) / .XLS malware analysis

Static analysis result for SHA-256 20a6cc4fc5bef1f8…

MALICIOUS

Office (OLE) / .XLS

61.5 KB Created: 2015-06-05 18:19:34 Authoring application: Microsoft Excel First seen: 2022-02-23
MD5: 8c1291da91ed9af5fb6f2d8a544a1c00 SHA-1: 7c9d5ed9bb78592f07bf019df537ae004faeffba SHA-256: 20a6cc4fc5bef1f877f0e93ada6ab979a5a5a0777869f50efc9eae0563fd9fcb
302 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1059.005 Service Execution: Visual Basic T1218.010 System Binary Proxy Execution: Regsvr32

The file contains Excel 4.0 macros, specifically an Auto_Open macro, which is a strong indicator of malicious intent. The macros are designed to execute 'regsvr32.exe' with a URL pointing to a payload. The ClamAV detection as 'Xls.Downloader.Emotet' further supports this classification. The reconstructed command line includes multiple URLs, suggesting a downloader functionality.

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 (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: Xls.Downloader.Emotet-ab81c42b2bd4747e-9951196-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.Emotet-ab81c42b2bd4747e-9951196-0
  • 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://littlesweet.co.uk/wp-admin/vko/
    • https://stratuswebsolutions.co.nz/wp-content/wyEEj5jH8xq50rp1/
    • http://wvfsbrasil.com.br/Acrasieae/LIYNOqCthfZuCWQz3/
    • https://lydt.cc/wp-includes/6sfYo/
    • http://lpm.fk.ub.ac.id/Fox-C/faKwS6p6/

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_macros.txt
0a554b35c45f3081eb2bd3af49bd7cee66f4b8ea0f2a41390fdd5477ea042fb4		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6618 bytes

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