When you say "probed by ransomware attacks" do you mean you visited a scary web page that said your computer is infected? Although unplugging your network cable, performing a system restore, removing the hard drive and smashing it with a sledge hammer would certainly be effective, it's also an ex-girlfriend batshit crazy obsessive way to deal with an accidental visit to a nefarious website. Whatever, just don't be one of those guys who tries to pile up four memory-resident antivirus suites for extra protection.
I certainly don't fault
@sholling for advocating 3rd party antivirus software, but personally I'm fine with Windows Defender. Some of the arguments
@TLS Guy offered are BS though. Defender doesn't have any advantage in extra-effective detection because it's integrated into the OS. It doesn't even have the highest detection rate. But for someone who keeps his OS, web browsers, and other software up to date; who employs uBlock Origin and OpenDNS filtering to help with avoiding treacherous websites; who is diligent about installing software only from reputable sources; who never opens unexpected email attachments or clicks unexpected emailed hyperlinks; and who doesn't experiment with dubious cracks and keygens; Windows Defender is good enough. In the rare cases I'm interested in launching an executable or opening a document about which I'm not 100% confident, I'll upload it to
www.virustotal.com for a second opinion. In other words, I think the best protection from viruses comes from responsible behavior.
In any case, I agree with
@sholling and
@TLS Guy that one should avoid choosing antivirus software that negatively impacts system performance. I strongly recommend against any software billing itself as a security suite. If it replaces Windows Firewall (which really can't be improved) and adds extensions to your web browser and email software, it's doing more harm than good -- at best as a waste of space, cpu cycles and money, and at worst by randomly denying net access to legitimate applications.