Windows: Windows Defender isn't the best antivirus software (even Microsoft admits its first-party solutions aren't ideal), but it's enabled by default on Windows 10 Home. In fact, the only way to disable it is to install something else. In a strange turn of events, Microsoft has made its Windows Defender feature a permanent fixture of Windows 10. You can temporarily disable it, as you see in the screenshot above, but you can't turn it off permanently. If it stays off for too long, Windows will turn it back on.
The one caveat to this rule, as pointed out by tips site MakeUseOf, is to install third-party antivirus software. Our pick for best antivirus software, Avira counts, as do most other major brands including BitDefender, AVG and Kaspersky. Once you install those applications, Windows Defender will disable itself. In other words, Microsoft doesn't really care which antivirus program you use, but you have to use something. On the one hand, this seems a little intrusive. On the other, how many of us have friends or relatives that refuse to take basic precautions, but still need help fixing their problems? If you really don't want to use any antivirus software, you can upgrade from Windows 10 Home to Professional. Unfortunately, you'll have to pay for the upgrade.