Hi, I kind of wonder if antivirus is necessary these days. I am inclined to believe there are threats on mac, so maybe it is not a bad idea to take precaution. Then I want to avoid some unknown or incomprehensible problem to me by downloading from Mac app store. Is this a good idea? Do you have some recommendations? It goes without saying that, I am not looking for an app that slows down the system significantly or cause problem to timemachine backup. I read about some of these in the past. BUt I haven't looked for a long time. If you can give me some idea, I thank you in advance.