I set up a linux desktop for my mom and at some point she told me "I have a virus, I tried to fix it but it didn't work".

Me: How do you know you have a virus?

Her: It told me

Me: Ummmmmm

I go look. She'd get a "fix your virus" popup and download whatever sketchy .exe file, but it couldn't launch. I think I added a ad blocker at some point, but not having the ability to launch whatever random exe she inadvertently download was a huge win for me.