It is feasible to prevent Tor users from accessing your service. This is by design. (see https://www.torproject.org/docs/faq-abuse.html.en#Bans https://www.torp

It is feasible to prevent Tor users from accessing your service. This is by design. (see https://www.torproject.org/docs/faq-abuse.html.en#Bans https://www.torproject.org/docs/faq-abuse.html.en#Bans) It is much harder to stop your users from accessing Tor. You can make it less convenient, but there are countermeasures. (see https://www.torproject.org/docs/bridges.html.en https://www.torproject.org/docs/bridges.html.en)