It is the opinion of several antivirus researchers and reviewers that Windows Defender has finally improved enough to be a more than adequate solution. However, PC Magazine's latest review notes that Windows Defender has the lowest aggregate score among antiviruses tested by four labs, AV-Test, SE Labs, AV-Comparatives, and MRG-Effitas.
Nonetheless, the reviewer does states, "We used to say Windows Defender is better than nothing. This time around, we're willing to say it's pretty darn good. Some of its lab test scores are excellent, though others aren't." He adds, however, "... the very best free antivirus utilities give you even more protection, and they earn great scores from the independent testing labs."