When to Replace Microsoft Defender

Microsoft Defender (previously Windows Defender), is Windows’ bundled antivirus software. It’s supplied free and installed by default; but is it any good and how do you know when to replace Microsoft Defender?

Microsoft/Windows Defender is a perfectly adequate anti-virus programme on Windows 10. For the home consumer, it works as well as all the other middle-market anti-virus programs. You can leave it running knowing that it is fully compatible with Windows 10 and will get regular updates of virus definitions and heuristics.

That said, when should you think about replacing it with another anti-virus product?

Two are not better than one

If you really think you need better protection such as an alternative or paid commercial anti-virus product, turn off Microsoft Defender and run with your new program as your single anti-virus software. Two do not protect you better than one. Owing to the way anti-virus programs constantly scan your device for suspicious activity and signs of malware in the file system, they will hog resources and interfere with each other, slowing down your machine and throwing hissy fits when they clash.

Windows Defender *can turn itself off if it detects another antivirus program running; but sometimes doesn’t. Best do this manually yourself.

Replace, don’t add


Anti-virus programs constantly run in the background to monitor file systems and traffic. This uses processor time, RAM and disk storage. They all do this, but Defender is known to be a little greedier than most. If you find you have performance issues with Defender running, it might be time to select an alternative with a smaller footprint better optimised for performance.

Periodic deep scans of the entire filesystem can be particularly egregious, bringing the machine to its knees while you’re trying to work.

Windows Update

Defender is frequently updated for virus definitions, but only as part of the regular Windows Update run for the whole of Windows 10. If you defer Windows Update – and there are good reasons why you might – this will also defer updates to Defender. Windows Update itself can also bug-out, stall and fail, which may mean your Defender virus updates get de-railed in the process, leaving you unprotected against newer threats.

Third party anti-virus programs run their own updates, more frequently on the whole than Defender. They don’t get stuck in the train with other Windows Updates like Defender.

Blocking Software installs

Windows Defender has a reputation for blocking installs of some software applications, particularly those that act as a local server processing streaming data such as online games. System utilities, especially file and data recovery tools also upset Defender because of the low-level permissions they require. Yes, you can whitelist applications if you can find the settings and choose the right ones in Defender to let them pass.

Third party anti-virus programs are generally less high-and-mighty and have a better white-listing and exception handling.


Microsoft Defender is a Microsoft product; you grant it full access to your local file system and potentially your entire network file system. And also your web-traffic. If you have concerns over how Microsoft uses this access to dial-home, update heuristics analysis or open secure files and folders, then replace it with a product that comes with assurances and guarantees from a supplier that is, shall we say, less cavalier with user’s data.

Replace, don’t just disable

By default, Windows Defender is your first line of defence against malicious software. DO NOT just disable it without installing an adequate replacement, or you leave yourself open to every threat, ‘bot and drive by attack on the Internet. AJS

2 thoughts on “When to Replace Microsoft Defender

  1. logereborn says:

    Thank you for these regular posts about Windows10. I find it to be such a dodgy system that I need these regular reassurances and/or warnings to set my mind at ease. This current post re Microsoft Defender would be even more helpful if it included instructions on checking/finding any other anti-v programs which might be clashing or causing delays. It seems that I have only MD installed.
    ps. My external HD for back-up is constantly becoming full. How do I know which back-ups to safely delete to make space?

    • Allan J. Smithie says:

      Installing a second A-V program isn’t the kind of thing you do by accident. Check your list of installed programs. Also, Defender is very good at flagging competing A-V software s that it can bully you into reclaiming its monopoly position.
      Backup strategy is an old familiar topic, it might be time to revisit in a new post.

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