Emotet — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 bc0c61366bf45113…

MALICIOUS

Office (OLE) / .XLSX

143.4 KB Created: 2022-01-26 02:21:30 Authoring application: Microsoft Excel
MD5: 0f80301041dca0bad8705f1011e010a3 SHA-1: ef603574762699c3ffa54cc0f912e4435cdc0b0e SHA-256: bc0c61366bf45113642db1e0f7c5d64e17d7d30cd994ce05f0de1d8de1386b0b
200 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1059.005 Visual Basic for Applications T1059.001 PowerShell T1204.002 Malicious File

The critical heuristics indicate the presence of Excel 4.0 macros with an Auto_Open function, specifically noting the use of dangerous APIs like RUN. ClamAV detection further confirms this as Emotet. The macro sheet is designed to execute code upon opening, likely to download and run a second-stage payload. The document content is a generic time card, serving as a lure.

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