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

Static analysis result for SHA-256 cfc40004d5b4d80d…

MALICIOUS

Office (OLE) / .XLSX

36.5 KB Created: 2020-11-27 11:42:42 Authoring application: Microsoft Excel
MD5: 120255c5abc187a34d107cb1fdb782d5 SHA-1: 518f80f6a551958ab61bc330e74ee6040fa98ca0 SHA-256: cfc40004d5b4d80d0d02187fe3dc5a6ac730ba597b2a677ff55681b53273c113
140 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1059.001 PowerShell T1059.003 Windows Command Shell

The file contains Excel 4.0 macros, specifically an Auto_Open defined name, which is a critical finding. This indicates that the macro will execute automatically when the workbook is opened. The presence of dangerous formula APIs like 'RUN' further confirms the malicious intent to execute arbitrary commands. The macro sheet itself contains a large amount of seemingly random data, likely obfuscation, but the core functionality is the auto-execution of commands.

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
ee03fb64265e95648aaafadb833178f8864dc8c043b48bba866ae11dd4b53b71
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6869 bytes