Office (OLE) / .XLSX malware analysis — malicious · b3517c4d50cdf56d

MALICIOUS

Office (OLE) / .XLSX

35.5 KB Created: 2020-11-25 10:40:05 Authoring application: Microsoft Excel

MD5: d5615aa7ebd573e67f01e62490863807 SHA-1: 5d56618b874348926901dd2cd735992c250b0baf SHA-256: b3517c4d50cdf56d44c5dabc9bd38ff7e0d6754357c734c2ff2c26089113d77d

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. No document body text was available for analysis, but the presence of the Auto_Open macro strongly implies a malicious intent to run external code.

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` `a074bd6586085ba2bc2279362491e39583b59102fe387b7f920ec5d4f5a4c3e7`	xlm-macro	oletools.olevba.extract_all_macros (XLM macro listing)	6448 bytes

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