Ok first of all I did a search and didn't find any topics similar to this but if there is one please delete it. My suggestion is to restrict users from posting links until they have a certain amount of posts. This way, those bots can't just join and add pages of links. Also it may keep some spammers (who don't use bots but just do the spamming themselves) away when they see the restriction. I've seen this used on other forums and I think it would be good here too.