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

Static analysis result for SHA-256 5b1f2076bb0aaff3…

MALICIOUS

Office (OLE) / .XLS

62.0 KB Created: 2006-09-16 00:00:00 Authoring application: Microsoft Excel
MD5: 5ddd4b615095fd9ee3b6fa503471b367 SHA-1: 3dd05ec2ced22790ba90432e447b80d3aa35a88d SHA-256: 5b1f2076bb0aaff3e5b2bb44f9e3e761719bf29d72caa25832ba7010444a48be
382 Risk Score

Malware Insights

MITRE ATT&CK
T1566.001 Spearphishing Attachment T1059.005 Visual Basic T1059.005 Visual Basic T1204.002 Malicious File T1105 Ingress Tool Transfer

The sample is an Excel 4.0 (XLM) macro-enabled spreadsheet that uses an Auto_Open macro to execute a series of commands. The Workbook_Open VBA macro also attempts to close the application. The XLM macros reference a URL, http://blog.vokasidev.com/crun20.gif, which is likely used to download and execute a second-stage payload. The presence of both VBA and XLM macros, along with the use of ShellExecute and URLDownloadToFile APIs, indicates a downloader or dropper functionality.

Heuristics 10

  • 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.
  • 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.
  • Reference to ShellExecute API high SC_STR_SHELLEXEC
    Reference to ShellExecute API
  • Workbook_Open macro high OLE_VBA_WBOPEN
    Workbook_Open macro
  • 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
  • Macro/content-enable lure medium SE_ENABLE_LURE
    Document instructs the user to enable macros or editing — a common technique used by malware droppers to bypass Office macro security settings
  • 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://blog.vokasidev.com/crun20.gif
    • http://blog.vokasidev.com/crun20.gif�

Extracted artifacts 2

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_macros.txt
d4222e1ad83b892546402a65bce1342319760d5f0e17d0c73ae5f07e792beb86		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 9447 bytes
macros.bas
c29faf2da8b6b84c63880f8f3ff09f138acdaa94ad9406cab75b546ae0e54428		 vba-macro oletools.olevba.extract_macros (decoded VBA source) 979 bytes

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