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

Static analysis result for SHA-256 66da1eaa6da6a2a5…

MALICIOUS

Office (OLE) / .XLS

315.5 KB Created: 2006-09-16 00:00:00 Authoring application: Microsoft Excel
MD5: 9f19e243c1aa35c2e35f43d25e7cc064 SHA-1: 4e5f2348fa3a177705941a9c6a142a7ccec5b916 SHA-256: 66da1eaa6da6a2a5b31f867d1b177df1b1f0788cf6d84012e420715d6af40736
262 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1566.001 Spearphishing Attachment

The sample is an Excel 4.0 macro-enabled workbook that uses an Auto_Open macro to execute. This macro is designed to download a second-stage payload from the URL https://nrdsbd.org/ds/0702.gif, which is presented as a link within the document body. The ClamAV detection name 'Doc.Downloader.Docusign0521-9864805-0' further supports its role as a downloader.

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 (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.
  • 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.
  • 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 https://nrdsbd.org/ds/0702.gif
    • https://nrdsbd.org/ds/0702.gif�

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_macros.txt
209c9794c827432fece79a7340e587efd134daeb8dd6093275d6099c9b2cbef4		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 3203 bytes

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