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

Static analysis result for SHA-256 72b4c11b5684b5f3…

MALICIOUS

Office (OLE) / .XLSX

36.0 KB Created: 2020-11-25 10:42:54 Authoring application: Microsoft Excel
MD5: 3c02effe5f7e6eb6965bcc5704324bc6 SHA-1: 019e0f567e1831ff54c92c13d14582cd6d448152 SHA-256: 72b4c11b5684b5f35cd8b5daac5d5a7ef1c225302c8bb47337dc1c884a946967
140 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1203 Exploitation for Client Execution

The critical heuristics indicate the presence of Excel 4.0 macros with an Auto_Open defined name, which is a known technique for executing malicious code upon opening the workbook. The macro sheet contains a call to a dangerous function, likely for command execution. No specific family could be identified, but the technique strongly suggests a downloader or initial execution stage.

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
7b1147468451f37c4da4ca6af586f456df906382cb8ab383484d0aac3278cd88		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6466 bytes

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