Microsoft is bringing its Defender antivirus software to iOS and Android, the company announced today. In fact, that's about all that it said on the subject, promising to demo the apps next week at RSA.
Microsoft Defender ATP (Advanced Threat Protection) is already available on macOS, and today, the public preview is coming to Linux. Microsoft says that Linux support has been a long-requested feature, so you can start testing it out today.
This is all a part of Microsoft's broader Microsoft 365 strategy. The firm wants you to be able to use Microsoft's services no matter what platform you're using, so that can obviously include macOS, Linux, Android, and iOS. Endpoint security is a major focus, as Microsoft considers itself to be in a better position than competitors to offer that.
As for Defender on iOS and Android, it's not clear what those solutions will actually do. Anyone that's familiar with iOS knows that there are some real limitations there, so it's possible that Defender could require you to use Microsoft services like Outlook, so it can provide phishing protection, and so on.