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

Static analysis result for SHA-256 2582c8b7f25a1162…

MALICIOUS

Office (OLE) / .XLSX

41.5 KB Created: 2020-11-25 10:24:32 Authoring application: Microsoft Excel
MD5: 34019ec92e4756aa46f0c6bbdb255e39 SHA-1: a24f8bf6ede893b9bd7d2c39796bc061647edabc SHA-256: 2582c8b7f25a1162407cba4715b86b930faec459aea3d2eb31f7ac2765bc464b
140 Risk Score

Malware Insights

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

The file contains Excel 4.0 macros, specifically an Auto_Open defined name, which is a critical finding. This indicates that the workbook is configured to automatically execute a macro when opened. The presence of dangerous formula APIs like RUN further suggests that the macro is intended to execute arbitrary commands. The macro sheet itself contains a large amount of obfuscated data, likely to hide the malicious payload. The Auto_Open macro is the primary mechanism for executing the malicious payload.

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
695aeb3ce6c461b1666f77b07395d7c55d2cfb4074d4ff8e8a16472fbc38bd00
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6642 bytes