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

Static analysis result for SHA-256 83625b9a4e8ec0f1…

MALICIOUS

Office (OLE) / .XLSX

36.0 KB Created: 2020-11-27 11:44:01 Authoring application: Microsoft Excel
MD5: d6b246c459ca1dc9b838cedb282c254f SHA-1: ca5f06c1bf3703738f94823dbda913cc6d207759 SHA-256: 83625b9a4e8ec0f1d09fb561c993651d9b37ab3dc94553c4b5039baf16569347
140 Risk Score

Malware Insights

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

The file contains Excel 4.0 macros, specifically an Auto_Open defined name, which is a critical finding indicating automatic execution upon opening. The presence of dangerous formula APIs like RUN suggests the macro is designed to execute arbitrary commands. The document body contains seemingly random strings and numbers, which could be obfuscated code or data for the macro. The primary IOCs are the sheet names, which are often used to hide macro code.

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
33a2a6643281daee63f554d4d788055e36fc01ccc8ff9dfcf3e41ee6e0909c65
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6781 bytes