It is very foolish not to use anti virus programs. Even the great websites one visits can be infected and they don't even know it. Therefor you won't know it. Because there are great FREE anti virus programs like MSE why would anybody take the chance?
I would 2nd that. I used Mac for years and even bought Nortons once cause someone said it helps to remove those malicous things from Universe, even if that do not have detremental effect on your specific computer Mac computer.
Finances have forced me to become PC user, but even before that, I helped my wife put in place MS defender Essentials couple of years ago.
I put in place right away on my new used Toshiba along with free Avast. Also use free Avast on wifes Mac, tho it won't scan the Mail.
So just inloaded Malwaebytes and just waiting to;
1) find out if Malwarbytes will play well with MSE defender, and free Avasti,
2) follow instructions to install if to see if it plays well.
Meanwhile, created FHNT(?) format on #3 partition of external HD I use for Mac cloning.
Inloaded Macricum also, but still unclear of what it showing me, so slow to try cloining( my preference ) or imaging. Some years ago, I heard that cloning is the best security we can do, at least on a Mac, so hope to get to that Macrium clone process today, with out erasing my other partitions of a clone Mac.
rsix