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

Static analysis result for SHA-256 815091132f54c240…

MALICIOUS

Office (OLE) / .XLS

330.5 KB Created: 2006-09-16 00:00:00 Authoring application: Microsoft Excel
MD5: 4eb51db360d7160752768c10d9dec9b1 SHA-1: 74a2239ecb329cae02c9ec491df7c9ce76c62729 SHA-256: 815091132f54c240c7d9dfe6ecf7c5c0e176296bed60c337538414410a03a826
302 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File T1566.001 Spearphishing Attachment

The file contains Excel 4.0 macros that are configured to automatically execute upon opening. These macros utilize the RUN function and CALL to execute a constructed string that appears to be a command to download and execute a payload from the URL https://rlink011.pw/ds/231120.gif. The presence of Auto_Open and the use of ShellExecute API calls strongly indicate a downloader functionality.

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 (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), across individual numeric cells (one ASCII charcode per cell), or split across multi-char fragment cells a download formula concatenates by reference (=A1&A2&… / CONCATENATE(...)). 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, LABELSST/RK/NUMBER cells, and FORMULA cell-reference concatenation in token order.
  • ClamAV: Doc.Downloader.Docusign0521-9864805-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Doc.Downloader.Docusign0521-9864805-0
  • Reference to ShellExecute API high SC_STR_SHELLEXEC
    Reference to ShellExecute API
  • 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://rlink011.pw/ds/231120.gif

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_macros.txt
c461ade38d400d4a423d855884def8ceb5c41198f9e35b0fb284854a9f7c58df		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6059 bytes

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