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

Static analysis result for SHA-256 4b25064a7d9d7d5f…

MALICIOUS

Office (OLE) / .XLSX

35.5 KB Created: 2020-11-27 11:46:34 Authoring application: Microsoft Excel
MD5: 88ecf8294352514ff6eeee347a48d874 SHA-1: 17b5f297e397c5f292c2e4a29bedbb73e2bcc329 SHA-256: 4b25064a7d9d7d5fa9368a1b8e26fa3d2cb17ba1d664b5ca825b695be3926b51
140 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1059.001 PowerShell T1059.003 Windows Command Shell

The file contains Excel 4.0 macros, specifically an Auto_Open defined name, which is a critical finding. The heuristics indicate that this Auto_Open macro uses dangerous formula APIs, including the RUN function, suggesting it is designed to execute arbitrary commands. The presence of the Auto_Open entry strongly implies the macro will execute automatically when the workbook is opened. The likely intent is to download and execute a second-stage payload.

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
60b262034fa8343d39b6dcca3925f5c6566f20d694169a9cbdd32e37efb8c6b3
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6861 bytes