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

Static analysis result for SHA-256 debca434af0c1151…

MALICIOUS

Office (OLE) / .XLSX

36.0 KB Created: 2020-11-25 10:39:02 Authoring application: Microsoft Excel
MD5: 5ab5bbfdb39adafdeae3c4f9132c5a25 SHA-1: 55f4ff215908ff9a0dbf1021e49d518c8c32b3b6 SHA-256: debca434af0c11517168c8c20ad279dfc27fb5962c515a112c1a5a7d182d2ae2
140 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Service Execution: Visual Basic T1059.001 Command and Scripting Interpreter: PowerShell T1059.003 Command and Scripting Interpreter: Windows Command Shell

The file contains Excel 4.0 macros, specifically an Auto_Open defined name, which is a critical finding. The presence of dangerous formula APIs like RUN within the Auto_Open macro indicates an intent to execute arbitrary code. This is a common technique for initial payload delivery in macro-based attacks. The macro sheet itself contains obfuscated data, suggesting an attempt to hide malicious activity.

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
789ab0323faa32f7e9412e6b8ad27518221fff2ec8566839a5392dfcad5c40e3
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6359 bytes