When we consider protection, we tend to think that more is better. In many cases this is true. Such as your car having locks plus an alarm, your money in a bank plus FDIC insurance on those bank deposits, or a 300+ pound center plus several large linesmen guarding your favorite quarterback on an important play.
Computer virus protection is different, and more than one application is actually much worse. They will fight one another in several ways, which can prevent the virus protection you need, and slow your computer down.
Anti-virus applications can be very “resource intensive”, meaning that they slow your computer down. All Anti-virus applications make your computer slower than it would be without them. Some anti-virus advertising campaigns brag about their product having less impact on performance than the competitors.
If you have more than one, not only are they both using resources and slowing you down, but they are actually fighting one another, and in some cases you may see dramatically slower computer speeds.
Each application you have running on your computer requires computing power, and the more you have running the less efficient each will be. Then, if you have applications that fight each other, it spirals into a very inefficient situation.
Many of my customers are unaware that they are running more than one anti-virus application and surprised at the difference it makes when we clean up the mess.
If more than one is not better, you might ask which is best. That depends on your specific needs. If you are a business that holds customer financial information, you will need more protection than a home user that seldom uses their computer. Do you primarily use your computer to check email, or are you checking your financial assets and retirement accounts? The latter needs more protection than the former.
Cost is an important factor. If you are a Comcast customer, they offer Norton for free. If you are an AT&T customer, they offer McAfee for free. Both of these provide respectable virus protection.
No matter what anti-virus you choose, be certain that you only have one installed. Any qualified computer tech can help you in this regard, and I would be happy to discuss your specific needs, and help you make the choice.