Office (OLE) / .XLSX malware analysis — malicious · f5cb3b309d859ced

MALICIOUS

Office (OLE) / .XLSX

36.0 KB Created: 2020-11-27 11:42:44 Authoring application: Microsoft Excel

MD5: cd0f35b213590c5e86aeca539718cf9c SHA-1: 7c51e96c70c681325041886e53657a35e4e08282 SHA-256: f5cb3b309d859ced92fbe10d5671b9ab939b986f2044d86aa05cedd5fc38396d

140 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1059.001 PowerShell T1059.003 Windows Command Shell

The file contains Excel 4.0 macros, specifically an Auto_Open defined name, which is a critical finding. The heuristics indicate the use of dangerous formula APIs, including the RUN function, suggesting the macro is designed to execute arbitrary commands. The presence of the RUN function is a strong indicator of malicious intent, likely 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.

Filename	Kind	Source	Size
`xlm_macros.txt` `5efd66067c74e1f37a7e1b8b7f969789277c7f4cdad53a994c32207953f33aa5`	xlm-macro	oletools.olevba.extract_all_macros (XLM macro listing)	6857 bytes

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