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

Static analysis result for SHA-256 957c75e9fdb179f2…

MALICIOUS

Office (OLE) / .XLSX

36.5 KB Created: 2020-11-25 10:44:23 Authoring application: Microsoft Excel
MD5: 15af656796471746d64631f45f41fda1 SHA-1: e35c7e29ba6cd4d5856ee81edfb70d5c3fcbb902 SHA-256: 957c75e9fdb179f23909fb11525f6c1d684d049655056be92f45ebc92c75d3ad
140 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1566.001 Spearphishing Attachment

The critical heuristics indicate the presence of Excel 4.0 macros with an Auto_Open defined name, which is a known technique for executing malicious code upon opening the document. The macro sheet contains a reference to 'Auto_Open', suggesting it will attempt to run code automatically. This is a common delivery mechanism for malware.

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
1e940d7fd61dd0e4b8cdeb9c2bc33fa644c7d959d980460c4e410b573aea71de		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6668 bytes

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