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

Static analysis result for SHA-256 806504c2f71327a3…

MALICIOUS

Office (OLE) / .XLSX

329.5 KB Created: 2006-09-16 00:00:00 Authoring application: Microsoft Excel
MD5: 36b5d980a88bef1fd5370336161cea71 SHA-1: fd0ccce493b7938f9ad6e508e6366e7a7c4725a8 SHA-256: 806504c2f71327a3fa9deba19f4602755a4943d7aa1a09b0e60e1df047ab5013
302 Risk Score

Malware Insights

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

The file contains Excel 4.0 macros, specifically an Auto_Open macro that utilizes the RUN function. This macro is designed to execute a URL, which is reconstructed as 'https://alpine.kz/ds/161120.gif'. This indicates the file's primary purpose is to act as a downloader for a secondary malicious payload. The presence of ShellExecute API references further supports this execution behavior.

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://alpine.kz/ds/161120.gif�
    • https://alpine.kz/ds/161120.gif

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_macros.txt
b74fbb14c9dd0283fe5b35630158622cf58bbddcd03d161d30bf64d1f40271a4		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 7889 bytes

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