This document contains anti-virus recommendations for home use.
Keep your Windows PC safe with trusted antivirus protection built-in to Windows 10. Windows Defender Antivirus delivers comprehensive, ongoing and real-time protection against software threats like viruses, malware and spyware across email, apps, the cloud, and the web.
Verify that your Windows 10 operating system is updated on your home PC: https://www.microsoft.com/en-us/windows/comprehensive-security
Open Windows Defender Windows Security Center on your PC: https://www.microsoft.com/en-us/windows/comprehensive-security
Note: You can only have one antivirus program running on your PC. If you have a paid antivirus program that is expired, it is no longer going to protect your computer, but it will also prevent Windows Defender from running. In that case, you either need to pay to renew your paid antivirus program, or you need to uninstall it so Windows Defender can be turned back on.
It is recommended that Mac users install antivirus, such as Sophos Home Free for Mac. There are many viruses designed for Macs, so they need antivirus. MacKeeper is fake antivirus, so do not install that one.
Make sure your Mac is up to date. It needs to be running the latest build of one of the three most recent major OS releases (as of April 2020 that's Catalina, Mojave, or High Sierra). You can verify what version you have by going to the Apple menu and selecing About This Mac. If you are on Mojave or newer, you can use Software Update in System Preferences to check for OS updates. If you are on High Sierra or older, you can use the App store to find updates.