Emotet — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 15f7a3c85d9986d0…

MALICIOUS

Office (OLE) / .XLSX

96.0 KB Created: 2015-06-05 18:19:34 Authoring application: Microsoft Excel First seen: 2022-07-12
MD5: 6a2e3d139fc00f750d4a56d38529da77 SHA-1: 788ff4191b16794334ce3faf0e50a4315e506e8e SHA-256: 15f7a3c85d9986d0e9501eeb81c8828f876a2f613efbf229949f329d953f6363
200 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1059.005 Visual Basic T1203 Exploitation for Client Execution

The sample is identified as malicious by ClamAV with the signature 'Xls.Downloader.Emotet-ea81817e7f807ab1-9952142-0'. Static analysis revealed the presence of Excel 4.0 macros, specifically an Auto_Open defined name, which is a known technique for executing malicious code upon opening the workbook. The heuristics indicate the use of dangerous formula APIs within these macros, suggesting the execution of a downloader.

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-ea81817e7f807ab1-9952142-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.Emotet-ea81817e7f807ab1-9952142-0
  • 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
44b7c45128c9ebff1e2d4c700363a400191ad3820db3f6fdcc49f6028eab1dc9		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 8173 bytes

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