Recently had a flatmate get DDOSed when he was gaming. Made our internet terrible until I spoke to our ISP who said we were DDOSed and they blocked my IP. They said it affects other customers and their whole network and if it happened again they would close our account. When asked how to stop it happening again they said there was no way apart from "be careful" and their only protection against it was closing my account if it happens again.
Firstly, what can I do on my end to ensure it doesn't happen again.
Secondly, why can an ISP in 2019 not have some form of protection against something that they said I can't stop happening and threaten to close my account?