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

Static analysis result for SHA-256 c40f8661b14cd6b0…

MALICIOUS

Office (OLE) / .XLSX

36.0 KB Created: 2020-11-25 10:31:46 Authoring application: Microsoft Excel
MD5: 84bbc092901734a15a7ec0022191d602 SHA-1: a39dfa0f93e1fa7730c4f85b7c1be89082c73ef6 SHA-256: c40f8661b14cd6b03bdefb41b9dde709ef4fc4b3a86b031003b6fe797661245d
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 triggering an Auto_Open function. Heuristics indicate the use of dangerous formula APIs, including the 'RUN' function, which is commonly used to execute arbitrary commands. This suggests the macro is designed to launch a secondary payload or perform malicious actions upon opening the spreadsheet.

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
7f3e3ed8593cbb392125ffeb1aac5e932ef19f4688a19e78514d0ddd1b5715fa		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6438 bytes

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