Emotet — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 579b9ca94b070e52…

MALICIOUS

Office (OLE) / .XLSX

106.5 KB Created: 2015-06-05 18:19:34 Authoring application: Microsoft Excel First seen: 2022-03-29
MD5: fde985939736724a304369094a406188 SHA-1: d1c59da1f667929772a27a83b810e5f6284d532f SHA-256: 579b9ca94b070e52e1ea611749b06a93fe22a1fc8f87746d1e27984f13bd00a9
262 Risk Score

Malware Insights

Emotet · confidence 95%

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

The file contains Excel 4.0 macros, specifically an Auto_Open macro that utilizes dangerous functions like RUN. The macros reconstruct and attempt to download payloads from six distinct URLs. ClamAV also identified the file as 'Xls.Downloader.Emotet-b2cbc93e36c0c13e-9950560-0', strongly suggesting an Emotet family infection. The reconstructed document body indicates the use of regsvr32.exe to execute a DLL, likely 'nhth.dll', from a downloaded payload.

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://fccatinsaat.com/wp-content/Cw3aR6792f/
    • http://fabulouswebdesign.net/invoice/m/
    • http://freemanylaluz.com/downloads/8dR9pgNBFtz/
    • https://freewebsitedirectory.com/wp-includes/v2qFAlMZELRkxbz/
    • http://futaba.youchien.net/wp-content/sSJqJ/
    • http://dominionai.org/wp-includes/T5qXAR8p5/

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_macros.txt
42fcced62e1b0500e019d401d9861bc8ead898ce0c99e4725ba96347a4a0e47e		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6551 bytes

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