Emotet — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 cdbaf3cb9709b655…

MALICIOUS

Office (OLE) / .XLSX

115.2 KB Created: 2022-01-24 14:50:55 Authoring application: Microsoft Excel
MD5: c557f21278ea2c46fe7fc8604aae0409 SHA-1: 5eafad6504fd0a5f9fa2fce47a64cc72c4c736c9 SHA-256: cdbaf3cb9709b6555c863cd587551e75c4541a6bda735d817dffc9cd911fa037
200 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1059.005 Visual Basic T1059.001 PowerShell T1566.002 Spearphishing Attachment

The critical heuristics indicate the presence of Excel 4.0 macros with an Auto_Open entry, specifically calling dangerous functions like RUN. ClamAV detection confirms this is Emotet, a known downloader family. The Auto_Open macro is designed to execute a second-stage payload, likely leveraging the RUN function to achieve this, which aligns with Emotet's typical behavior.

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
f65423032a2492710482664c048191ebe835ee4ace2752f1b0fa6e40d416cdf9
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 4885 bytes