Office (OLE) / .XLSX malware analysis — malicious · 34ca8c0daff7dd3b

MALICIOUS

Office (OLE) / .XLSX

36.0 KB Created: 2020-11-25 10:41:37 Authoring application: Microsoft Excel

MD5: dc72c5140b5572f935a6ca895958db87 SHA-1: 9b0d3d45aa0863d8306ca5d1e5e52b85693a5cbc SHA-256: 34ca8c0daff7dd3b424f23735bbba04c2a2c1ca0388ef29daeed0aec00bd0a38

140 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic for Applications T1566.001 Spearphishing Attachment

The sample contains Excel 4.0 macros, specifically an Auto_Open defined name, which is a critical finding. This indicates that the workbook is configured to automatically execute a macro when opened. The presence of dangerous formula APIs like 'RUN' further confirms the malicious intent to execute arbitrary code. No specific family could be identified, but the technique is commonly used for initial access.

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.

Filename	Kind	Source	Size
`xlm_macros.txt` `d5556ae348e829e08288a13f46cb22f0dcec04ac34f34a928991cb18636536e5`	xlm-macro	oletools.olevba.extract_all_macros (XLM macro listing)	6601 bytes

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