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

Static analysis result for SHA-256 d03b1d500e960377…

MALICIOUS

Office (OLE) / .XLSX

124.5 KB Created: 2015-06-05 18:19:34 Authoring application: Microsoft Excel
MD5: e090402a8daf077e501420ddb825fde5 SHA-1: 1d18d06935d7f16fb2008599b4c607b7f341ebc4 SHA-256: d03b1d500e960377df77a72c5074b4c56b29f938f48ecd03ac846b38d3c914d3
242 Risk Score

Malware Insights

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

The sample is an Excel 4.0 macro-enabled spreadsheet that uses an Auto_Open macro to execute. It impersonates a document signing service (DocuSign) to trick the user into enabling macros. The macro reconstructs a URL, 'http://URLMonURLDownloadToFileArundll,DllRegisterServe', which is likely used to download and execute a second-stage payload. The presence of the 'SE_DOCUSIGN_LURE' heuristic further supports the social engineering aspect.

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) 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.
  • 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
  • Document signing service impersonation lure medium SE_DOCUSIGN_LURE
    Document impersonates DocuSign, Adobe Sign, or a similar signing service in a signing-request context
  • 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

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_macros.txt
4faf3105ecc2aac884cbb8f1af11f65b7e22c01c59a885436f8fe1fac847737b		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 7003 bytes

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