Emotet — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 1b846e1ffb7b04dd…

MALICIOUS

Office (OLE) / .XLSX

142.3 KB Created: 2022-01-26 02:21:30 Authoring application: Microsoft Excel
MD5: 0ae1be69313edb9f619f07cfa5201dbb SHA-1: 71711bf848f2bb618ea66710396ad59d4649fdcd SHA-256: 1b846e1ffb7b04dd60200cc3741fa3a341f9a8cf982a974b596eab20804917a5
200 Risk Score

Malware Insights

Emotet · confidence 95%

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

The file is detected as malicious by ClamAV with the signature Xls.Downloader.Emotet-bd646319c2d29cd6-9951195-0. Heuristics indicate the presence of Excel 4.0 macros, specifically an Auto_Open function that utilizes dangerous formula APIs, including the RUN function. This strongly suggests the macro is designed to download and execute a secondary payload, a common Emotet distribution technique.

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

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