(Neil J. Rubenking @ PC) Early adopters, daredevils, and purchasers of new computers are all running Windows 10 by now. Those who err on the side of caution, or whose IT department forbids them to, are still running Windows 8. Whether you run Windows 8 or Windows 10, your computer is theoretically under the protection of the built-in Microsoft Windows Defender. However, our hands-on tests and independent lab tests show that you're better off with a third-party solution. Fortunately, you've got plenty of free choices, and the best of them are better than many competing commercial products. Which one is best for you? We've rounded them up to help you choose.

Quite a few of these products are free only for noncommercial use; if you want to protect your business, you have to pony up for the paid edition. At that point, you should probably consider upgrading to a fullsecurity suite. After all, it's your business's security on the line. And if you've grown beyond SMB status, investing in a SaaS endpoint protection system will let you monitor and manage security across your entire organization.

See Our Top Paid Antivirus Solutions

Your antivirus should definitely have the ability to root out existing malware, but its ongoing task is to prevent ransomware, botnets, Trojans, and other types of nasty programs from getting a foothold. All of the antivirus programs in this collection offer real-time protection against malware attack. Some take the fight upstream, working hard to ensure you never even browse to a malware-hosting site, or get fooled into turning over your credentials to a phishing site.

Independent Antivirus Lab Test Results

Around the world, researchers at independent antivirus testing labs spend their days putting antivirus tools to the test. Some of these labs regularly release public reports on their findings. I follow five such labs closely: AV-Comparatives, AV-Test Institute, Simon Edwards Labs(the successor to Dennis Technology Labs), Virus Bulletin, and MRG-Effitas. I also take note of whether vendors have contracted for certification by ICSA Labs and West Coast Labs.

Security companies typically pay for the privilege of being included in testing. In return, the labs supply them with detailed reports that can help improve their products. The number of labs that include a particular vendor serves as a measure of significance. In each case, the lab considered the product important enough to test, and the vendor felt the price was worthwhile. The labs don't necessarily test a vendor's free product, but most vendors pack full protection into the free product, enhancing premium versions with additional features.

PCMag Antivirus Test Results

In addition to carefully perusing results from the independent labs, I also run my own hands-on malware blocking test. I expose each antivirus to a collection of malware samples, including a variety of different malware types, and note its reaction. Typically the antivirus will wipe out most of the samples on sight, and detect some of the remaining ones when I try to launch them. I derive a malware blocking score from 0 to 10 points based on how thoroughly the antivirus protects the test system from these samples.

Since I use the same samples month after month, the malware-blocking test definitely doesn't measure a product's ability to detect brand-new threats. In a separate test, I attempt to download malware from 100 very new malicious URLs supplied by MRG-Effitas, typically less than a day old. I note whether the antivirus blocked all access to the URL, wiped out the malicious payload during download, or did nothing. Avira Free Antivirus holds the current top score in this test, followed by McAfee and Symantec, both paid products.

If you're interested in learning more about my testing techniques, you're welcome to read more about how we test security software.

Useful Features

Just about every antivirus product scans files on access to make sure malware can't launch, and also scans the entire system on demand, or on a schedule you set. Once that cleaning and scheduling is done, blocking all access to malware-hosting URLs is another good way to avoid trouble. Many products extend that protection to also steer users away from fraudulent websites, phishing sites that try to steal login credentials for financial sites and other sensitive sites. A few rate links in search results, flagging any dangerous or iffy ones.

Behavior-based detection, a feature of some antivirus products, is a two-edged sword. On the one hand, it can detect malware that's never been seen before. On the other hand, if it's not done right, it can baffle the user with messages about perfectly legitimate programs.

One easy way to keep your PC protected is to install all security updates, both for Windows and for browsers and other popular applications. Windows 10 makes it easier than ever to stay up to date, but there are plenty of security holes in older Windows versions, in popular apps, and in add-ons. Scanning for vulnerabilities in the form of missing updates is a feature most often found in commercial antivirus products, but it does turn up in some free ones. In the chart above you can see which products include these useful features.

What's Not Here

This article reports only on free antivirus products that received at least a good rating in our reviews—three stars or better. Among those that didn't make the cut is Microsoft Windows Defender, with 2.5 stars. All of the independent labs I follow do include Microsoft in testing, but most use it as a baseline. If a product can't do better than the baseline, it's got real problems.

FortiClient fans may notice that this product doesn't appear in chart. It did get three stars, but it's quite different from the rest. FortiClient is actually designed to work as a client for Fortinet's network security appliance, but is incidentally available as a free standalone.

Furthermore, I'm aware that my review of Bitdefender's Free Antivirus is getting long in the tooth, but the company simply doesn't update its free utilities as often as its premium ones. Rest assured, I'm in close contact with Bitdefender and I'll review its new offering when it becomes available. Now that the commercial Bitdefender 2017 line is out, perhaps the developers will have more time to work on the free edition.

There are also numerous free antivirus utilities that work solely to clean up existing malware infestations. You bring out these cleanup-only tools when you have a nasty malware infestation. When the problem's gone, they have no further use, since they offer no ongoing protection. Our Editors' Choice in this category is Malwarebytes Anti-Malware 2.0, and it's definitely one you should try if you've got a malware problem. But since they're free, you can keep trying others if the first one doesn't do the job. When the scare is over, you'll need a full-blown antivirus for ongoing protection.

What's Best

Our current Editors' Choice products for free antivirus utility are Avast Free Antivirus, AVG AntiVirus Free, and Panda Free Antivirus. All three get very good scores from the independent labs, and in our own tests as well. All three include some useful bonus features. Avast in particular packs a password manager and a network security scanner in its toolkit. If you do have a little cash in your budget for security, the best paid antivirus products do tend to offer more and better protection. If not, try a few of these free tools and see which one you like best.