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

Static analysis result for SHA-256 b91bd79e54b47998…

MALICIOUS

Office (OLE) / .XLSX

36.0 KB Created: 2020-11-25 10:32:50 Authoring application: Microsoft Excel First seen: 2023-03-30
MD5: f7a5636823fa8f31ead3c2acab3fb999 SHA-1: d755bc88892cfb653e6c8fb1b05637af916aa22a SHA-256: b91bd79e54b479982cc3dbe9eb1ca22b2c91595e80ffc758c06ba54eb0ee4650
140 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1059.001 PowerShell T1204.002 Malicious File

The critical heuristics indicate the presence of Excel 4.0 macros with an Auto_Open defined name, specifically calling the RUN function. This strongly suggests the macro is designed to execute a command or payload upon opening the spreadsheet. While the exact command is not fully recoverable from the provided script excerpt, the technique is commonly used for initial access and malware delivery.

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
2663453d55f3d8b3b3b00cdc62819b176b8667c7c336a66a8c3264eef0546e67
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6360 bytes