Emotet — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 83f08a62f298a538…

MALICIOUS

Office (OLE) / .XLSX

142.5 KB Created: 2022-01-26 02:21:30 Authoring application: Microsoft Excel
MD5: cdbcb0643356075b907823a8cf388e02 SHA-1: 17aa47a63b8b98a43c5bb4af0ee0f02d11f7fd18 SHA-256: 83f08a62f298a538c63f10fbe9e68717a2f38f1226f27644525ab2ecf4a7b72a
200 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, specifically noting the use of dangerous formula APIs like RUN. ClamAV detection confirms this as Emotet. The macro sheet is designed to execute code upon opening, likely to download and run a secondary payload, consistent with Emotet's typical behavior. The document content is a plausible lure for a time card.

Heuristics 4

  • 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.
  • ClamAV: Xls.Downloader.Emotet-bd646319c2d29cd6-9951195-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.Emotet-bd646319c2d29cd6-9951195-0
  • 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
46284ea41c691066b9fe85a87bc7e9bfc77336182ea3b4ed700574b0c8cd3189
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 3141 bytes