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

Static analysis result for SHA-256 bdbf676a1c0b0822…

MALICIOUS

Office (OLE) / .XLSX

36.0 KB Created: 2020-11-27 11:44:35 Authoring application: Microsoft Excel
MD5: b3f04c2025de45cb6c4b20258e56b592 SHA-1: ca825bc0cc44ef400fbed48f27776370d0a2a167 SHA-256: bdbf676a1c0b08223b49abb2067d9e32a6738b1a7001c821e6e919dd489a2e4d
140 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic

The file contains Excel 4.0 macros, specifically an Auto_Open defined name, which is a critical heuristic firing. This indicates that the macro sheet is designed to automatically execute code upon opening the workbook. The presence of dangerous formula APIs like RUN further supports the malicious intent. The macro sheet itself is heavily obfuscated, making it difficult to determine the exact payload, but the Auto_Open function is a clear indicator of an attack pattern designed to run arbitrary 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
ce92d299ad67f2e9efe7e47f6fb92c337a00c5beea5722adada58cee07c56a54
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6596 bytes