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

Static analysis result for SHA-256 18fc35ecdc63acee…

MALICIOUS

Office (OLE) / .XLSX

36.0 KB Created: 2020-11-25 10:44:37 Authoring application: Microsoft Excel
MD5: 2cd387f8ac05467b7d2294ad5e73fee0 SHA-1: e2519fbae1306cb6da3ff2676a7954d60c82da6f SHA-256: 18fc35ecdc63acee0b1961e75902114b855a14f2cadf5c1ccea1f67baf43a4ee
140 Risk Score

Malware Insights

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

The sample is an Excel file containing Excel 4.0 macros, indicated by the OLE_XLM_AUTOOPEN and OLE_XLM_DANGEROUS_FN heuristics. The presence of an Auto_Open defined name suggests that the macro will execute automatically when the workbook is opened. The dangerous formula API 'RUN' (0) is also present, which is commonly used to execute arbitrary code or download additional payloads. No specific URLs or hashes were extracted, but the technique strongly implies a downloader or initial execution 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
1565bdc7ea404edfc2d1202df2be3ea0b7325e98078a2d7d994176b1b2cd9f71
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6352 bytes