Malicious Office (OLE) / .XLSX — malware analysis report

Static analysis result for SHA-256 df2fd3061bf48cb2…

MALICIOUS

Office (OLE) / .XLSX

325.0 KB Created: 2006-09-16 00:00:00 Authoring application: Microsoft Excel
MD5: 521ee8bf226e4926983bc4cde5127391 SHA-1: b075d6513e7e5dd3e1701f16b1bfcf1d690df570 SHA-256: df2fd3061bf48cb2b4fa4d91651f6136fc3d00468edfc2440e76c93d54e655d7
340 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File T1059.001 PowerShell T1105 Ingress Tool Transfer

The sample contains both Excel 4.0 (XLM) macros and VBA macros, with the XLM macro sheet containing an Auto_Open entry that calls a function named 'RUN(Tenr.Viurni)'. The VBA macro defines a function 'Viurni' which uses URLDownloadToFile to download a file from the reconstructed URL 'https://demex.ro/ds/1712.gif' to a path specified in Sheets("Docs3").Range("AA13"). This indicates a downloader functionality, likely to fetch and execute a second-stage payload. The ClamAV detection 'Doc.Downloader.Docusign0521-9864805-0' further supports this, along with the presence of 'DocuSign' in the sheet names and document body.

Heuristics 7

  • Reference to URLDownloadToFile API critical SC_STR_URLDOWNLOAD
    Reference to URLDownloadToFile API
  • 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.
  • URLDownloadToFile in VBA critical OLE_VBA_DOWNLOAD
    URLDownloadToFile in VBA
  • ClamAV: Doc.Downloader.Docusign0521-9864805-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Doc.Downloader.Docusign0521-9864805-0
  • 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.
  • VBA macros detected medium OLE_VBA_MACROS
    Document contains VBA macro code

Extracted artifacts 2

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_macros.txt
6d105297a3a4cfdc5c7c8c3cc101ee970587957a058bce962f4bc5360b4e8f8f		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 1686 bytes
macros.bas
bdd3b85e07b194d2432d5db1744d79ca82727bd20a6ccf84313354c0dfd8f7a8		 vba-macro oletools.olevba.extract_macros (decoded VBA source) 2017 bytes

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