Office (OLE) / .XLSX malware analysis — malicious · 3a27df27123dfe41

MALICIOUS

Office (OLE) / .XLSX

35.5 KB Created: 2020-11-25 10:25:18 Authoring application: Microsoft Excel First seen: 2023-03-30

MD5: 379146831e96c4374f3d05db46d978b2 SHA-1: 9e7d1e8042810ee3b691ee307caed7dd5fd0577d SHA-256: 3a27df27123dfe41e25bfbbabd52dc78fd6a7dd9c569dd4464a60eca621623e1

140 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1059.001 PowerShell

The file contains Excel 4.0 macros, specifically an Auto_Open function, which is a known method for executing malicious code upon opening the workbook. The critical heuristics indicate the presence of dangerous formula APIs like RUN, suggesting the macro is designed to download and execute a secondary payload. The document body contains heavily obfuscated text, which is typical for lures in macro-based attacks.

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` `63d6238631e7996c7adbab35856c26b26ab102c6c8c10c73c9983b022a742fa4`	xlm-macro	oletools.olevba.extract_all_macros (XLM macro listing)	6413 bytes

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