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

Static analysis result for SHA-256 50640611dbd7b83e…

MALICIOUS

Office (OLE) / .XLSX

36.0 KB Created: 2020-11-27 11:40:51 Authoring application: Microsoft Excel
MD5: 1ede5c4d227a47299ae5f7d22b2fe897 SHA-1: 58a54aa5bbcaa298981aadb931074900396b4255 SHA-256: 50640611dbd7b83e639727859ce0fc9f44e2e8c5b5da32467bef764c99ca4ac5
140 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic for Applications T1059.001 PowerShell

The sample contains Excel 4.0 (XLM) macro sheets with an Auto_Open defined name, indicating that malicious code will execute automatically when the workbook is opened. The critical heuristics indicate the presence of dangerous formula APIs, specifically the RUN function, which is commonly used to execute arbitrary commands or download additional payloads. No specific family could be identified, but the technique is indicative of a downloader or initial access 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
c4dd1623f54c681503c010afe54b50b0139cf348239b7fa14f797ad2a0a81546
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6835 bytes