Let me chime in on this, first thing first, I see infected computers among other things on a regular basis. I have been doing this a very long time. I will never let a computer leave my shop without some level of protection. I personally would not suggest having a windows box without some kind of protection PERIOD. If you are a careful and skilled person and want to roll the dice, feel free, but for the average end user VERY bad advise. I do agree with the fact that most new variants of malware, ransom ware and viruses will blow by your antivirus program on occasion but it happens to all of them from time to time, just the nature of the beast.
I just helped a guy with 7 of his office computers, All got the same e-mail about a Fed Ex International item ready to be picked up. It seemed the office computers had a wide range of different antivirus programs. Here is how they did. Updated Nortons 360 fail, AVG..Fail , The windows 7 boxes all got infected and all there data was encrypted. The window 10 boxes running just windows defender..well it stopped it in its track. A example of human nature to click. No matter how careful people are, the odds are not in your favor long term.
I can understand this and agree with this. But wouldn't you say there is no way of really knowing if you have a virus or not ? I mean if your antivirus says you have one it could be a false positive, but let's say that it is a real virus and the antivirus program cleans it , you do a scan and it says your clean how do you really know your clean? You wouldn't know your 100% clean unless you format and reload from a known good source like Microsoft web site. And I do think you should run the antivirus that comes with windows I'm not saying turn that off. This is why I wouldn't give a windows machine to someone who just wants to surf the web and Facebook or check email. Just give that user a chromebook. But if Wanna run BI you obviously need windows. Point is windows is only needed in certain situations.