If you use a desktop or laptop computer, you absolutely need to have antivirus software installed, and this goes for both Windows and Mac OS machines.
There are a lot of options, and most of the major ones—Norton, McAfee, Bitdefender, Trend Micro—do a good job if you keep them updated and active. In just about every case, that means paying an annual fee, which usually falls between $20 and $40 per year for a personal computer. Compared to the time and expense of fixing a compromised computer, however, it's a pretty good deal.
However, it is also important to know how antivirus software actually behaves once installed. You've heard of Tech Support phone scams in which a caller claiming to represent Microsoft tries to convince the victim to follow instructions that lead to fraudulent credit card charges, a hacked computer, or both, but there are also websites that will display popup windows in an attempt to accomplish the same objective.
When you have real, paid-for antivirus software installed, for the most part it runs quietly in the background. It may give you a message when you start your computer, but other than that, you will generally only hear from it if you try to download or install an infected file or if your subscription is about to run out.
What will NOT happen is a popup window telling you "your PC is infected!" or "your PC is ____% damaged" or "WARNING! YOUR COMPUTER MAY BE INFECTED" with instructions to enter a credit card number or call a phone number, or to click a "Repair Now" or "Free Virus Scan" button. Those are all coming from a compromised website you're visiting.
If you are already paying for antivirus software, that's where the payments stop. You do not pay extra to have viruses removed—detecting and removing malware is what you're paying for in the first place. You also will never speak to a live person on the phone. If your antivirus software detects a problem, it will deal with that problem.
If you get one of these popups, all you have to do is close your browser window, don't click anything on the popup window itself, and consider avoiding whatever website you were visiting that generated the popup in the first place.
