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

Static analysis result for SHA-256 72c8440f05813851…

MALICIOUS

Office (OLE) / .XLSX

36.0 KB Created: 2020-11-25 10:46:30 Authoring application: Microsoft Excel
MD5: d5d6ee7878a08bf3218e70b2e1d65700 SHA-1: e879a4c5abfce94254d79ac2b91db5bd8ec95db9 SHA-256: 72c8440f05813851d58ef224d8f569e70dfb731100d854adfea21fca8ce35c8f
140 Risk Score

Malware Insights

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

The file is an Excel spreadsheet containing Excel 4.0 macros, indicated by the OLE_XLM_AUTOOPEN and OLE_XLM_DANGEROUS_FN heuristic firings. The presence of an Auto_Open defined name suggests that the macro will execute automatically when the workbook is opened. The dangerous formula APIs used, specifically RUN, point to the execution of arbitrary code, likely to download and execute a second-stage payload. No specific family could be identified.

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
623c0e238951c67b1b5dde74014d5c451188d6beda1cb8ec7655e3767e74ed58
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6502 bytes