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

Static analysis result for SHA-256 3c7fc3c26f7829f6…

MALICIOUS

Office (OLE) / .XLSX

36.5 KB Created: 2020-11-25 10:38:55 Authoring application: Microsoft Excel
MD5: de47dece7aad8066557902782c3ab142 SHA-1: f6d45483253abcb233a9c5a5c7819f059b44070e SHA-256: 3c7fc3c26f7829f69680b1e91b7f860f9c2afd112e3e7d83cfc8027c3357cd67
140 Risk Score

Malware Insights

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

This Excel file contains Excel 4.0 (XLM) macros, specifically an Auto_Open macro. The presence of dangerous formula APIs like RUN indicates that the macro is designed to execute arbitrary commands. The macro sheet itself contains a large amount of obfuscated data, suggesting it's used to hide the actual payload or execution logic. The primary attack vector is the Auto_Open macro, which is a common method for initial execution of malicious code in older Excel formats.

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
3244f21444f4f54ecbd7436a01399c58366696bb31d41ff8e2a4d43699c80712		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6499 bytes

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