Emotet — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 f3101b6d16751623…

MALICIOUS

Office (OLE) / .XLSX

106.5 KB Created: 2015-06-05 18:19:34 Authoring application: Microsoft Excel First seen: 2022-03-30
MD5: aaab4929ca9090b91c0ba04783b712ce SHA-1: f6fed487c6fa398825c17c2dd1add6b31449125e SHA-256: f3101b6d16751623f8a025bfbf75ae9a32c68b534dccbab4452ee72a9fbe0f5f
262 Risk Score

Malware Insights

Emotet · confidence 95%

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

The file contains Excel 4.0 macros with an Auto_Open entry, which is a known technique for executing malicious code. The macros reconstruct and attempt to download payloads from multiple URLs, including 'http://dmcontabilidade.com/correspondentecaixa/TrS/'. The presence of 'regsvr32.exe' in the macro further suggests the execution of downloaded payloads. ClamAV detection confirms this as Emotet.

Heuristics 6

  • 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.
  • URL reconstructed from XLM cell array (6 URLs) critical OLE_XLM_CELL_ARRAY_URL
    Excel 4.0 macro sheet stages its payload URL across the BIFF8 Shared String Table (one quoted-char SST entry concatenated with & at runtime) or across individual numeric cells (one ASCII charcode per cell). The reconstructed URL is invisible to literal-bytes URL extraction because it is never contiguous in the workbook stream. URLs were recovered by walking the BIFF8 record stream and decoding SST entries plus LABELSST/RK/NUMBER cells.
  • ClamAV: Xls.Downloader.Emotet-b2cbc93e36c0c13e-9950560-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.Emotet-b2cbc93e36c0c13e-9950560-0
  • 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.
  • Embedded URL info EMBEDDED_URL
    One or more URLs were extracted from the document. The URL itself is not a detection — see the per-URL labels for which channel (macro, JS, link annotation, document body, ...) reached each URL.
    URL http://dmcontabilidade.com/correspondentecaixa/TrS/
    • https://fcelik.nl/rittenregistratie/web/css/B3ILfU8Xk2SsEmT/
    • https://www.gessersh.com/wp-includes/ZwQLepW/
    • https://www.fantasticmotion.jp/_cnskin/qfWEQrrwBg/
    • http://fanfield.co.uk/cgi-bin/7pp6DjWFNJXY8/
    • http://www.garantihaliyikama.com/wp-admin/FjgB6I/

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_macros.txt
feeff176628c881d9521dcd3ca882317ecc22390c60a180eb94dc7523ff8eda0		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6551 bytes

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