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

Static analysis result for SHA-256 b32a801cf080f147…

MALICIOUS

Office (OLE) / .XLSX

36.0 KB Created: 2020-11-25 10:42:21 Authoring application: Microsoft Excel
MD5: 755897b3334aaa5635e913a50647b8b4 SHA-1: ecc0c42247767afc4e0b4ae123cec43492cd5dea SHA-256: b32a801cf080f1478fba5a2674e91d0a98b1a0316b1612b8a9b55bbf70ee1df6
140 Risk Score

Malware Insights

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

The sample is an Excel file containing Excel 4.0 macros, specifically an Auto_Open macro. 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 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
12f697e98b26e4050ed11a741dfbae8132b67ce0551af765d99f05e9cd402307		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6527 bytes

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