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

Static analysis result for SHA-256 2cff74ae72dbd54f…

MALICIOUS

Office (OLE) / .XLSX

88.5 KB Created: 2020-05-20 08:20:55 Authoring application: Microsoft Excel
MD5: 40c9d108ebe2cb69eb6ea8852137e092 SHA-1: cf023074db318b5d515d7767ec96a64f9009e0f4 SHA-256: 2cff74ae72dbd54fee18ac4817c5ebb8c846b00b8f9aaff816aef53d5f41c949
140 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic for Applications T1204.002 User Execution: Malicious File T1105 Ingress Tool Transfer

The sample is an Excel workbook containing Excel 4.0 (XLM) macros. Heuristics indicate the presence of an Auto_Open macro that utilizes dangerous formula APIs (RUN), which is a common pattern for executing arbitrary commands. The document body contains a heavily obfuscated string that appears to be a a URL (http://os.meduarncbxC\DGVqBLjySRPY...), which likely serves as the C2 server for the payload delivery. No scripts were extracted from the sample, but the XLM macro structure is supporting the execution flow.

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
b3cbcd65f46810650897d0067f294b5cac5bb35287fe8ea3e66219cb1086a49d		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 58038 bytes

Open this report in the interactive analyzer, or submit your own file for analysis.