I've been using Windows long enough to remember when installing antivirus software felt like one of the first things you had to do on a new PC. You set up Windows, installed your browser, and then immediately went looking for something to protect the whole thing before you did anything even slightly risky online. It wasn't paranoia, either. For a long time, Windows had a reputation for being the platform malware loved most, and running without some kind of extra protection felt like asking for trouble.