Emotet — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 17f902ec7a5d598b…

MALICIOUS

Office (OLE) / .XLSX

96.0 KB Created: 2015-06-05 18:19:34 Authoring application: Microsoft Excel First seen: 2022-07-12
MD5: 4d11257c23a70749087f0203eb3e0275 SHA-1: 4630a14dfda56e8ef9db76c752b322f2af8bba30 SHA-256: 17f902ec7a5d598b6ecbe50765367fc29a02812af76cb2a188e4d09f5c1b49b9
200 Risk Score

Malware Insights

Emotet · confidence 95%

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

The sample is identified as malicious by ClamAV and exhibits critical heuristic firings indicating the presence of Excel 4.0 macros with an Auto_Open entry. These macros utilize dangerous functions, suggesting an intent to download and execute a second-stage payload, consistent with Emotet's typical behavior. The presence of an Auto_Open macro in an Excel file strongly implies it was delivered as a spearphishing attachment.

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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