Software Windows

How good is Windows Defender?

Windows Defender
Strong defence? Find out if Windows Defender is up to it

If you run a Windows 10 or Windows 11 PC, you might well be wondering which antivirus software package to use on it. Both versions of Windows build in Microsoft’s own security suite, Windows Defender, but is it good enough to rely on? First we’ll reveal how good Windows Defender is at stopping malware and then show you how to activate it on Windows 10 and Windows 11 if you decide to stick with it.

Is Windows Defender good enough?

When Microsoft started bundling its own security software with Windows – it was called Microsoft Security Essentials in those days – it had a pretty ropey reputation. However, Windows Defender (as it is now known) competes very well with even paid-for security suites.

Let’s look at the independent evidence from three different security software testers:


AV-Comparatives conducts regular tests of all the major Windows security software packages, including software from Kaspersky, McAfee and Norton. In the latest test at the time of writing (December 2021), AV-Comparatives gave Microsoft Defender its highest three-star ranking for protection.

The AV-Comparatives results show Windows Defender blocked 99.7% of the threats thrown at it in the company’s tests, and didn’t raise any false alarms at all. It did let through two threats, but that’s two in many hundreds of such attempts.


Those results are backed up by AV-Test, who also give Windows Defender a ‘Top Product’ rating for its October 2021 tests (although an awful lot of other products get that award too). On AV-Test’s report card, Defender scored 100% protection against new (or zero-day) threats in both September and October, and it gave 100% protection against known threats in October, with 99.9% protection in September. It’s also worth noting that Windows Defender scores well in these tests for the minimal impact it has on PC performance.

SE Labs

Finally, SE Labs – run by my former colleague Simon Edwards – posts a third set of positive results for Windows Defender. The SE Labs consumer test for the third quarter of 2021 ranked Defender as the second best security product overall, with a protection accuracy rating of 96% and a perfect record when it came to reporting false positives.

As Simon himself said in a recent tweet: “We test [Windows Defender] regularly… it has improved a lot.”

Windows Defender verdict

No security product is flawless, but the strong results in three independent tests suggest Windows Defender is more than good enough to rely on for antivirus protection. Other free and paid-for products may offer additional features, such as VPNs and online backup, but Defender is fine for day-to-day protection.

How to activate Windows Defender in Windows 10 and Windows 11

Time needed: 10 minutes

Step-by-step guide to activating Windows Defender in Windows 10 and Windows 11

  1. Remove other antivirus software

    Before you activate Windows Defender, you need to make sure you’ve uninstalled any other security software on your computer to avoid conflicts. Indeed, Defender may refuse to run if it detects other antivirus software on the PC. To uninstall existing software, search for ‘remove’ in Windows 10 search, select ‘Add or remove programs’ and remove any existing security programs. You will likely face a barrage of warnings about doing so and you may need to restart your PC at the end of the process. Once complete, proceed to step 2.

  2. Open Windows Security

    Search for ‘security’ and open the Windows Security app that appears in the search results.

  3. Ensure all options are switched on

    Now make sure that you’ve got green ticks showing against the five main categories here: virus & threat protection, account protection, firewall & network protection, app & browser control, and device security. If you haven’t got a tick, click the option to enable these features. The screenshot shown below is from Windows 10, but Windows 11 is near identical and the three steps here are exactly the same.Windows Defender in Windows 10

About the author

Barry Collins

Barry has scribbled about tech for almost 20 years for The Sunday Times, PC Pro, WebUser, Which? and many others. He was once Deputy Editor of Mail Online and remains in therapy to this day. Email Barry at

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  • I liked your comments on Lenovo Vantage. I do not use Defender because it is another way MS can collect data which can go directly to NSA