Yes, Microsoft Windows Defender is an antivirus service. It is a built-in security feature of the Windows operating system that provides protection against malware, viruses, and other online threats.

Windows Defender was first introduced in Windows Vista as a basic antivirus program. It has since been improved and expanded, and it now provides a more comprehensive range of security features. These include:

• Real-time protection: Windows Defender constantly monitors your computer for signs of malware activity and takes action to block or remove threats when they are detected.
• Malware scanning: Windows Defender can scan your computer for known malware signatures and also use heuristic algorithms to identify suspicious behaviour that may indicate the presence of malware.
• Cloud-based protection: Windows Defender uses cloud technology to share threat information with other Windows users, which allows it to provide up-to-date protection against the latest threats.
• Automatic updates: Windows Defender receives regular updates from Microsoft to ensure that it is able to protect against the latest threats.

Overall, Microsoft Windows Defender is a reliable and effective antivirus service that provides protection against a wide range of malware threats. It is a convenient and cost-effective option for users of the Windows operating system.