From a performance impact standpoint, based on just one test suite, it is the worst on the market. https://www.av-comparatives.org/tests/performance-test-octob

From a performance impact standpoint, based on just one test suite, it is the worst on the market. https://www.av-comparatives.org/tests/performance-test-october-2019/ https://www.av-comparatives.org/tests/performance-test-octob... (and I linked to the same article in your parents comment...) Avira and Bitdefender manage to rank in the top tier of performance impact and protection every time I check. Both offer free products, and Bitdefender Free is considerably less annoying, in my past experiences. Free antivirus is actually one of the places where market competition forced a bunch of them to clean up their acts and offer a good non invasive product. Avira still has ads, but if you wanted one product on your pc and one on a home server, it might make sense to use two vendors products. https://www.bitdefender.com/solutions/free.html https://www.bitdefender.com/solutions/free.html https://www.avira.com/en/free-antivirus-windows https://www.avira.com/en/free-antivirus-windows For one off system scans, besides the two mentioned above; ESET, F-Secure, Kaspersky, Panda (and Emsisoft which has Avira and Bitdefender built in) all offer great spot check products. ADWCleaner is indispensable. It's interesting that "anti-virus" has now become the free component in suites. You pay for things like VPN, password management, and home network security. Kaspersky goes a step further and offers VPN and password management in a free tier. https://usa.kaspersky.com/free-antivirus https://usa.kaspersky.com/free-antivirus