Windows Defender does cover the easy 80% of the market on that platform.<p>But modern malware is so far beyond traditional anti-virus programs that we have to start talking about entire new schools of thought on what constitutes a program, and what is desirable or not.<p>If you look at the AV Comparatives reviews, some programs have traditionally done well in the anti-virus space, like Kaspersky, Avast, etc.... But these days, I think we have to ask ourselves if we are willing to trust a Russian company to perform anti-virus scanning on our systems, or if that “cure” is worse than the disease.<p>So far, the one program I’ve seen that has done well in the comparisons and is also relatively light weight in impact on your systems resources, is Malware Bytes. And it seems to work well on Windows as well as macOS. So, I continue to recommend and use it on all my systems that I control.<p>But that still only covers a small part of the much broader field of undesirable programs, despite the name of the package. You have to include other tools as well, like outbound network firewalls for data loss protection, programs that monitor in real-time for activities that look like file encryption, etc.....<p>On macOS, I look to programs from <a href="https://obdev.at/products/index.html" rel="nofollow">https://obdev.at/products/index.html</a> and <a href="https://www.objective-see.com/products.html" rel="nofollow">https://www.objective-see.com/products.html</a> to help with these additional areas of security concern.<p>And I do my backups, both local and remote.