Should I Use Multiple Antivirus Programs?

Multiple Antivirus Programs - A Good Idea?

Often when you buy a new computer, it comes with a trial version of Norton, McAfee or some other commercial antivirus software. When that free trial is about to expire, the program starts to nag you about upgrading to a paid version, which can be expensive. That's when some users start looking for an antivirus alternative. There are some excellent free and paid options, but a common mistake is to install a new one without removing the old one. Some users also think they'll be more secure if they install a second antivirus program.

In most cases, having more than one antivirus program running on your computer is bad news. While the idea of doubling up on security might seeem like a good idea, it can lead to significant system problems, that will reduce, rather than increase, your computer's protection from viruses and malware.

Antivirus programs are designed to operate deep into a system's core, monitoring processes, files, and network activities at the "kernel" level to detect threats in real time. They also consume significant memory and processing power, as they scan the streams of data, emails, web pages and downloads that attempt to enter your computer.

So it makes sense that having more than one antivirus scanner will slow down your computer. But as mentioned above, slower performance may be the least of your problems when more than one security tool is vying for supremacy. While competing for the same low-level operating system monitoring points, antivirus programs can interfere with each other's operation. This may lead to one or both failing to intercept threats, missing malware, or even exposing security loopholes.

This could happen without you knowing, or it could manifest in the form of error messages, or the dreaded Blue Screen of Death. (On Windows 11, it's the Black Screen of Death. See Farewell, Blue Screen of Death?)

Another issue is the potential for false positives and unwarranted quarantine. One antivirus may identify the operations of the other as suspicious, leading to confusing false alarms, and unintentional quarantining of legitimate programs or files.

The Antivirus Death Spiral

But there's another potential problem... sometimes antivirus programs can fight with each other, since they both want to be the final arbiter of good and evil on your computer. One might even think the other *is* a virus, and attempt to disable it.

I actually tested this scenario once, installing the free versions of Avast, Avira, and Bitdefender anti-virus on my computer all at once. The result was a computer that slowed to a crawl. You could watch paint dry between keystrokes, and the process of uninstalling them took hours. I refer to this as the "antivirus death spiral" wherein each contender is thinking that the other is trying to do something bad, and unsuccessfully try to prevent it.

My advice is to pick ONE antivirus tool and stick with it, at least until you decide to replace it with another. There are some good free options, as I mentioned above. But free software can come with strings and conditions. That can mean compromising your privacy, or dealing with endless nagging to upgrade to a paid subscription that includes all the features you need to be truly safe online.

After years of using Avast Antivirus, I switched to PC Matic, which uses a unique combination of protection strategies that I think are superior. You can read my review and recommendation in PC Matic 4.0 – My Review

Exceptions to the Rule

That said, let me introduce just a bit of tech talk, and explain the exceptions to my single anti-virus rule. There are three types of anti-virus protection: real-time, on-demand and offline. Here's a quick description of each:

The real-time variety we've been discussing so far protects against viruses and other threats as they arise. Your real-time anti-virus software is constantly scanning everything that enters your computer, as well as every program that runs. Some examples are Norton, McAfee, Avast, BitDefender, and many others. You only want ONE of these active.

On-demand virus scanners are only active when you specifically launch them, to perform a one-time scan of your system for malware. Some popular options are HitmanPro, Emsisoft Emergency Kit, and SuperAntiSpyware. On demand scanners are designed to co-exist with your real-time anti-virus software, and can sometimes catch things that have slipped through your first line of defense. You may need to pause your current protection before running an on-demand scanner.

Offline anti-virus tools run from a bootable CD or flash drive, and will do a deep scan of your computer. While the offline scanner is running, both Windows and your primary anti-virus program are inactive. See Extra Security: Offline Malware Scanners for more info on offline security tools.

So to be clear, YES, I recommend just one REAL-TIME security tool. Supplementing that with an on-demand scanner is fine. And for those situations where you can't start up your computer due to a virus infection, an offline scanner is what you need.

Which Antivirus Programs Do I Have?

If you're not terribly tech savvy, you might not even know which antivirus program is installed on your computer, if you have more than one, or none at all. To find out if you have antivirus protection, click Start, type Windows Security, and press Enter. The name of your anti-virus product will be listed under the Virus and Threat Protection heading. If you see anything other than green checkmarks on the Windows Security screen, you need to install, activate, or update your anti-virus software.

On Windows 10 and 11, Microsoft Defender is the built-in antivirus protection. It runs automatically, and disables itself when another securtity tool is installed, reducing risk of unintentional conflict.

Next, go to the Control Panel and click Programs and Features. Look for names such as AVG, Avira, Avast, BitDefender, Eset, F-Secure, G Data, Kaspersky, McAfee, Norton, Panda, or Trend Micro. If you find more than one, go to Control Panel, Add/Remove Programs, and uninstall the anti-virus program(s) you don't want to keep. (Bear in mind what I mentioned about real-time and on-demand scanners above.) You'll need to restart your computer to finish the removal process. When you're done, make sure your remaining antivirus protection is up to date and run a complete scan to check for nasties.

Do you have something to say about anti-virus protection? Post your comment or question below...