Emotet — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 423c9fe2d7c27c2f…

MALICIOUS

Office (OLE) / .XLSX

70.9 KB Created: 2022-01-20 19:00:43 Authoring application: Microsoft Excel
MD5: 283ca17b8df03a554fb8d402c8064c33 SHA-1: b438a0342a82e7bd20aef4423b90fda31a7159ad SHA-256: 423c9fe2d7c27c2f91785e754d0281d61626e45074695a9ad965ea73bba4b93c
140 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1059.005 Visual Basic T1566.001 Spearphishing Attachment

The critical heuristics indicate the presence of Excel 4.0 macros with an Auto_Open entry, a known technique for Emotet. ClamAV detection further supports this attribution. The macro sheet contains an Auto_Open defined name, suggesting it will execute automatically when the workbook is opened. This is a common delivery mechanism for Emotet, which typically downloads and executes a second-stage payload.

Heuristics 3

  • 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.
  • ClamAV: Doc.Downloader.EmotetExcel01220-9937164-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Doc.Downloader.EmotetExcel01220-9937164-0
  • 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.

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_macros.txt
7f1f89a8b36a750dced08313a4e4f056192a6eac7194357c673dbbd2670a1a18		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 4219 bytes

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