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

Static analysis result for SHA-256 b783c140073714ce…

MALICIOUS

Office (OLE) / .XLSX

36.5 KB Created: 2020-11-27 11:41:14 Authoring application: Microsoft Excel
MD5: 6818b7272403792c94aee74e10c7e566 SHA-1: 1b089c9c3033845c2791281b0e1479f4c7cc4845 SHA-256: b783c140073714cef20db819df7678c0d2f459ffcafe5fb3d858506b257d4edb
140 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1059.001 PowerShell

The sample is an Excel file containing Excel 4.0 (XLM) macros, specifically an Auto_Open macro. This indicates an attempt to automatically execute code when the workbook is opened. The presence of dangerous formula APIs like RUN suggests the macro is intended to download and execute a second-stage payload. No specific family could be identified, but the technique is common for initial access.

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
77cc790918d2118406e3351d51de3cbe862ab134b0ba4abfaba3ea575a087827		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6911 bytes

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