What about firing up a very simple script on a machine behind a squid proxy?
Teh proxy can and will if set to do so deny all access to such pages (hackers, porn, warez, etc.) with a nice big red "ACCESS DENIED" image page. But hey, it blocks doubleclick.com as well :-)
Anyhow, could it be simpler?

Have a nice day
All decision is left to your taste