Is Windows Defender sufficient?

[OFaceSIG]

Windows Defender in combination with Open DNS, throw in some general common sense possessed by the user - and I feel that is sufficient.

I run ClamAV at the network layer in my pfsense box. Windows defender on any win10 boxes, AVGfree on my remaining 7 box. That plus what was said above, some good internet hygiene, and you'll be fine.