Emotet — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 b5d8116e0b4f01eb…

MALICIOUS

Office (OLE) / .XLSX

113.0 KB Created: 2015-06-05 18:19:34 Authoring application: Microsoft Excel
MD5: ac2e55c6ebc2e750550b4191b9777dea SHA-1: 9bcdcce969a1a3b95d88b81854f59e20ced6a99c SHA-256: b5d8116e0b4f01eb2affa09d857d1be4df2e18dd793e4ab0b6ad28e0d5eadc15
302 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1059.005 Visual Basic T1218.011 System Binary Proxy Execution: Rundll32 T1059.001 PowerShell

The file contains Excel 4.0 macros, specifically an Auto_Open macro, which is a critical indicator of malicious intent. The macros are designed to execute a command using 'rundll32.exe' to download a payload from one of the embedded URLs. The ClamAV detection and the presence of multiple suspicious URLs further support the malicious classification. The reconstructed command is 'rundll32.exe "http://gaidov.bg/wp-includes/Ug/","7"'.

Heuristics 7

  • 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 (3 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-bd646319c2d29cd6-9951195-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.Emotet-bd646319c2d29cd6-9951195-0
  • LOLBin token sequence in document text high SE_LOLBIN_RUN_COMMAND
    Extracted document text contains a Windows script/execution tool name (PowerShell, mshta, cmd, rundll32, regsvr32, …) within 220 characters of a dangerous flag, command verb, or URL. This is a visible 'run this' instruction in HTML/PDF/RTF lure bodies, or — in macro-laden Office files — the macro's own string-pool entries appearing adjacent in extracted text.
  • 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://gaidov.bg/wp-includes/Ug/
    • http://goodmarketinggroup.com/live_site/Y9cEk9QNlDUeg/
    • http://studiokrishnaproduction.com/wp-includes/3mJ/

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_macros.txt
4d32d4bc18234076b76fff05a9ee50b43b756f16fa43d7a1a9cb0b5c555b4ddf		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 4504 bytes

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