Office (OLE) / .XLSX malware analysis — malicious · 9a28e13a36fc5cce

MALICIOUS

Office (OLE) / .XLSX

36.0 KB Created: 2020-11-25 10:44:40 Authoring application: Microsoft Excel

MD5: fbe5d4c848610f31cf46b7a7a56724bd SHA-1: e9426bd3ca1cb3fd11c7b12119ccae4d9b40d00c SHA-256: 9a28e13a36fc5ccedd023a4722f35c2567e8354cd0b13e67888c7a0d7fea2dd8

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 presence of the RUN function within these macros indicates an attempt to execute arbitrary code. This strongly suggests the file is designed to download and execute a second-stage payload. The document body contains a large amount of seemingly random characters, which could be obfuscation or part of the macro's execution.

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` `f4bb200328e0522dc8f4675948109d0001727460904870841b2152c9341dbcf6`	xlm-macro	oletools.olevba.extract_all_macros (XLM macro listing)	6472 bytes

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