Malware Bytes is highly regarded. I use it on some of my systems, and compared to BitDefender, it seems to protect my systems equally well, but with much lower operational impact. It’s not uncommon for BitDefender to turn my machine into a jet engine for certain periods of the day, while it’s doing COU intensive stuff.<p>I’ll be switching all of my machines to Malware Bytes, when it comes time for subscription renewal.
GateKeeper, MRT (Malware Removal Tool), and XProtect are all built-in features of Mac OS designed to prevent malware threats and other nefarious software from being installed or used on a Mac. These security features exist in the background and are updated with regular system software updates to Mac OS, but Apple will also push quiet updates to xprotect or MRT to add new definitions and block newfound threats.