There was a lot of debate about introducing Windows Defender, Microsoft's built-in antivirus, to other operating systems, notably smartphones, before the company released Windows 11.
After more than a year, Microsoft has chosen to relaunch the program under the name Microsoft Defender, although it will not perform the functions you anticipate.
Microsoft Defender for iOS and macOS will not be an antivirus, but rather a tool to warn users about harmful websites and a window to monitor the security state of other devices.
On Windows, it won't be much different, since the software will merely display the user's AntiVirus subscriptions in order to avoid interfering with Windows Defender.
The app's sole significant value will be on Android.
The program will function as an anti-virus and malware detector, alerting users to potentially harmful websites.
Worst of all, this service will be offered only to Microsoft 365 members, who get Office apps and cloud storage.