Emotet — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 c8a0330bcd3b208d…

MALICIOUS

Office (OLE) / .XLSX

109.0 KB Created: 2015-06-05 18:19:34 Authoring application: Microsoft Excel
MD5: 4aa82f81ac87593a64538a66b7deef21 SHA-1: 6ac03f72868d6ff2f95e517729ae4a6e3ce018bc SHA-256: c8a0330bcd3b208d6f7e63eacfd7f3052149b5ae523d1c5337e8a901fa71df22
262 Risk Score

Malware Insights

Emotet · confidence 95%

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

The file contains Excel 4.0 macros, specifically an Auto_Open macro, which is a known technique for executing malicious code. The macros reconstruct and utilize multiple URLs to download and execute a secondary payload. ClamAV detection further confirms its malicious nature as Doc.Downloader.EmotetExcel02220. The reconstructed URLs are the primary indicators of compromise.

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 (5 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: Doc.Downloader.EmotetExcel02220-9938626-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Doc.Downloader.EmotetExcel02220-9938626-0
  • 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://arzulens.com/wp-includes/7gySgTg/
    • https://simplinteriors.com/wp-admin/B1e/
    • https://www.swaong.com/wp-admin/k9Db4Vjafnk/
    • http://68bets.site/b/bL2bq71qNY/
    • https://farocf.com/wp-admin/rX9FcCxf0Cf4bj/

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_macros.txt
50aac6306d81f77d2140d85b020a980d4c24646f532e5d63efea2f839d07ed30		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6315 bytes

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