Windows Defender, now known as Microsoft Defender Antivirus, is a built-in security solution in Windows operating systems designed to protect computers from malware, viruses, spyware, and other malicious software. It offers real-time protection by monitoring files and applications to detect and block threats immediately. Users can perform quick, full, or custom scans to identify and remove malware from their systems.

One of its key features is cloud-delivered protection, which utilizes cloud intelligence to detect new and emerging threats more quickly. Advanced threat detection capabilities are powered by machine learning and behavioral analysis, enhancing its effectiveness against various types of malware. Windows Defender integrates with Windows Firewall to provide network protection against unauthorized access and includes ransomware protection through controlled folder access, preventing unauthorized changes to files.

The user interface is simple and user-friendly, displaying security status, recent scans, and any detected threats, along with recommendations for improving system security and privacy settings. As a part of the Windows operating system, it seamlessly integrates with other security features like Windows Firewall and Windows Hello. Regular updates through Windows Update ensure that Windows Defender can effectively combat the latest threats.