You will not be able to efficiently automate finding trolls with an algorithm. You may accidentally catch some trolls with it, but this is not really the same as the algorithm <i>working</i> - with a large enough userbase you could randomly ban accounts and probably catch a few trolls as well, given a flexible enough definition of "troll."<p>What you will accomplish with an automated filter is a way for trolls to game the system (that is what actual trolls do), and an excuse for human mods, if you have them, not to care (or worse, to game it themselves in order to censor legitimate posters.) "Future banned user?" How wonderfully fascistic. If you can read that term and feel it's a good way to describe new users to your whatever community, do everyone else a favor and, please, give someone else the banhammer.