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

Static analysis result for SHA-256 093fbc79451f5d02…

MALICIOUS

Office (OLE) / .XLSX

36.5 KB Created: 2020-11-27 11:39:06 Authoring application: Microsoft Excel
MD5: 7f136dc6bc04c622d0b46c59bca650f6 SHA-1: 23cb02ae43a1346b0f5acc3c8ff016e04e59a5aa SHA-256: 093fbc79451f5d02d08fa3a36383fa8e38d7210d61626b4e485d22f63fdc14d4
140 Risk Score

Malware Insights

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

The file contains critical heuristics indicating the presence of Excel 4.0 macros, specifically an Auto_Open function. This function is designed to execute arbitrary code upon opening the workbook, which is a common technique for downloading and executing further malicious content. The macro sheet itself contains obfuscated data, suggesting an attempt to hide its malicious intent.

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
fa73e18f69b31837f71aa1d7931e90e0f9b3a71bfce23ca79bda77fe9bd8ff62		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6739 bytes

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