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

Static analysis result for SHA-256 857be31492e667e2…

MALICIOUS

Office (OLE) / .XLSX

36.0 KB Created: 2020-11-25 10:43:22 Authoring application: Microsoft Excel
MD5: d3382eb4bcc01460e21d2c18b89e13bd SHA-1: 8cf5ea8746bd3164b96c1567026084b3b794d1aa SHA-256: 857be31492e667e2c3e22afda694d495774bfc33fce1fb2e70c6d12e91d7ebc5
140 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1566.001 Spearphishing Attachment

The file contains Excel 4.0 macros, specifically an Auto_Open defined name, which is a critical finding. This indicates the macro sheet is designed to execute code automatically upon opening. The presence of dangerous formula APIs like RUN further confirms the malicious intent to execute arbitrary code. No specific family could be identified, but the technique is common for initial execution.

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
ec5c267bdd10b9288ae26dc714df5610f430ed6f1fb7345b33d9f69dff9b4bb9		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6553 bytes

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