If you use a Mac, you do not need an antivirus service like Norton. They burrow deep into your operating system in an effort to protect your device, but they themselves might be vulnerable if not perfectly crafted. There aren't many macOS viruses, and anti-malware updates quickly take care of the few that pop up behind the scenes. Antivirus products will probably slow your computer down, sometimes considerably, in order to operate. In fact, Apple may have even blocked applications that dig so suspiciously deep into their OS.