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

Static analysis result for SHA-256 c3879cebb88e6c20…

MALICIOUS

Office (OLE) / .XLSX

35.5 KB Created: 2020-11-25 10:26:03 Authoring application: Microsoft Excel
MD5: 2f86a153b60bd4be355e1fbc62370fb9 SHA-1: 0a3e442204f87481aa0ac79b5d029b5567a5d228 SHA-256: c3879cebb88e6c20b307f7ac0f65788c380870b20ab14468b27b037caf75481b
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 function, which is a critical indicator of malicious intent. The presence of 'RUN=0' in the heuristic firing suggests the macro is designed to execute a command or program. While the specific command is not fully visible, the Auto_Open macro is a common technique for initial execution and payload download. The document body contains heavily obfuscated text, which is typical for lures in macro-based attacks.

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
982b92a2d496d8b351925acb06bac975853f5fd82ade642b8a979cd28f468cac
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6422 bytes