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

Static analysis result for SHA-256 159d4ad702a0b51a…

MALICIOUS

Office (OLE) / .XLSX

193.5 KB Created: 2015-06-05 18:19:34 Authoring application: Microsoft Excel
MD5: e314a7660e275bde15719f4060d0b8b9 SHA-1: 55563ad26ce201da3ea1b6ada781a1feee7593e5 SHA-256: 159d4ad702a0b51a2821dd0c637ceb0fcbdcb19bb2d8d299e648fc88b049511c
202 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1203 Exploitation for Client Execution

The file contains Excel 4.0 macros, including an Auto_Open function that utilizes dangerous APIs like RUN. The macros are designed to download a payload from the URL 'http://URLMonURLDownloadToFileArundll,DllRegisterServe' and execute it. The presence of the Auto_Open macro and the download functionality strongly suggests a malicious downloader.

Heuristics 5

  • 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 (1 URL) 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.
  • 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://URLMonURLDownloadToFileArundll,DllRegisterServe
    • http://www.iec.ch
    • http://ns.adobe.com/xap/1.0/
    • http://www.w3.org/1999/02/22-rdf-syntax-ns#
    • http://purl.org/dc/elements/1.1/
    • http://ns.adobe.com/xap/1.0/mm/
    • http://ns.adobe.com/xap/1.0/sType/ResourceEvent#
    • http://ns.adobe.com/xap/1.0/sType/ResourceRef#
    • http://ns.adobe.com/photoshop/1.0/

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_macros.txt
732bfa752b66213cfed6fb95799054a82ee4bf330cc7b9914a7ec49aa3f08d0f		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 12026 bytes

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