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

Static analysis result for SHA-256 6cf0a44011ec1e1a…

MALICIOUS

Office (OLE) / .XLS

124.5 KB Created: 2015-06-05 18:19:34 Authoring application: Microsoft Excel
MD5: 2739a59d758db92aafa95fa723456172 SHA-1: 5466fe009cf7ee11393085ebd99c16963d49eb0a SHA-256: 6cf0a44011ec1e1a891d7d06357c4687634e42d65a3eecfe9180e608b5d6e150
242 Risk Score

Malware Insights

MITRE ATT&CK
T1566.001 Spearphishing Attachment T1059.005 Visual Basic T1203 Exploitation for Client Execution

The sample is an Excel file containing Excel 4.0 macros, specifically an Auto_Open macro designed to execute automatically. It impersonates a document signing service to trick the user into enabling macros. The macro then uses the URL 'http://digitaldays.ro/site/brandupi.' to download a second-stage payload, likely leveraging the 'URLMonURLDownloadToFileArundll,DllRegisterServe' 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) 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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