It's going to be an on-going cat mouse game. Reading more it seems that the end game is not to push traffic to the site(s) linked from the posts but to have the URLs in the posts picked up by the search engine BOTs that crawl the boards for info. The more posts with your URL in them, the higher your site is in the search engine rankings
Poking around, one tool that I came across (
http://www.xrumer.co/) boasts more than 4 million active BBS links and the ability to bypass a lot of technologies to limit un-authorized posts. I've watched videos of spam software and with the right software, you generate thousands of posts in a matter of minutes. I'm not a BBS admin but work in IT so it's always a good idea to keep your software up to date as it will eliminate a lot (but not all) of the problems.
Diane