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

Static analysis result for SHA-256 d90ed7ce6f1c738b…

MALICIOUS

Office (OLE) / .XLSX

36.0 KB Created: 2020-11-25 10:40:34 Authoring application: Microsoft Excel
MD5: c6a4bfc42bc6876faa38e6d72e170e4f SHA-1: 3145a08102491da8f93ab5263246c4fc0e3df804 SHA-256: d90ed7ce6f1c738b683a2f9b317988b24f06ea3cecabacd6eb8989bf0934c947
140 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1059.001 PowerShell T1204.002 Malicious File

The critical heuristic OLE_XLM_AUTOOPEN_DEFINEDNAME indicates the presence of an Excel 4.0 Auto_Open macro. This macro is designed to execute automatically when the workbook is opened. The critical heuristic OLE_XLM_DANGEROUS_FN further confirms that dangerous formula APIs, specifically 'RUN=0', are used within this macro, which is a strong indicator of malicious intent to execute arbitrary code. The macro sheet itself contains a large amount of seemingly random data, typical of obfuscated macro code or embedded payloads.

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
d2d8fefd70478b374d61193a78dbfb4cfa6ab8152484791dec8a071f20809025
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6362 bytes