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

Static analysis result for SHA-256 b86fbb13e480a468…

MALICIOUS

Office (OLE) / .XLSX

36.0 KB Created: 2020-11-27 11:39:25 Authoring application: Microsoft Excel
MD5: 211ac570b721c3f46959aefbe46a65ab SHA-1: 6d644c5aa6223fd92332727f2122f4929b629efd SHA-256: b86fbb13e480a4686a08d2e7e83c20b572b88c4b6b6869a8edc3fa4d14963d73
140 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic

The critical heuristics indicate the presence of Excel 4.0 macros with an Auto_Open function, which is a known method for executing malicious code. The macro sheet is named 'rfOrbvCxllUE' and contains a defined name for Auto_Open, suggesting it will run automatically when the workbook is opened. The document body contains a large amount of seemingly random data, likely obfuscated macro code or payload.

Heuristics 3

  • 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.
  • 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.

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_macros.txt
3de56a85cbd3b6816a80eb4ab87b69af48968a382ec93ee89a61035cf190097d		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6987 bytes

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