Office (OLE) / .XLSX malware analysis — malicious · 3915358ded936307

MALICIOUS

Office (OLE) / .XLSX

36.5 KB Created: 2020-11-25 17:35:09 Authoring application: Microsoft Excel

MD5: 391a0c52310d629f268ec99380d5a77d SHA-1: 30d6cb702cf97b63f57df091af2f51ea80f51faf SHA-256: 3915358ded93630775825ac14e7303fabdc1020adf89dc65a4cd82947c104ab7

140 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1059.001 PowerShell

The sample contains Excel 4.0 macros, specifically an Auto_Open defined name, which is a critical heuristic firing. This indicates that the workbook is configured to automatically execute a macro when opened. The presence of dangerous formula APIs like RUN further suggests malicious intent, likely to download and execute a second-stage payload. No specific family could be identified, but the technique is common 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` `780dd22f097ca34b001c1d9feb495fd433e9684273d55e040e5a94bc23cd0c6d`	xlm-macro	oletools.olevba.extract_all_macros (XLM macro listing)	6664 bytes

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