Look at your router and see if it can do this. It would be a lot better to block at a centralized router for all the machines being fed under it, then to have to try to maintain a block list at each machine. Routers are inexpensive enough that if your current router does not do this, that you might want to replace it with a router that does.
Don't forget to block not only the hostname, but the ip address and ipaddress range that it represents.
Hope that helps,