Have one but never needed it so far - or it didn't catch the virii ;)

I use bitdefender at least it's quite unobtrusive on mac (sick of the windows version!). Sophos is free and afaik not too bad if you need one: https://home.sophos.com/free-mac-antivirus

Further I use: - https://objective-see.com/products/knockknock.html - https://objective-see.com/products/oversight.html - https://objective-see.com/products/blockblock.html

and Little Snitch - https://www.obdev.at/products/littlesnitch/index.html

and Firefox with - https://github.com/gorhill/uMatrix - https://github.com/gorhill/ublock

Hope that keeps the pest away ;)