I had used one of those hacks that block urls in posts before but the problem was that the true spammers would stick the url in the thread title and/or in their profile etc. Basically anywhere except in the post. The result was we still got spammed AND it irritated normal members who weren't spamming but were unfortunate enough to be in that low-level usergroup. In the end I removed it and spent hours going through user profiles and editing threads removing spam urls. If your hack stops users in one particular usergroup from posting urls ANYWHERE in the forum, then I'm interested.