Stop the Robot Invasion

As has been recently discussed, there's a lot of spam in the Offtopic forum lately (it's not in any other forums, is it?). I was wondering if there are any changes that could be implemented that would prevent so many spambots from registering to the board and posting? Are there any CAPTCHA's involved nowadays in the registration process? Finding some way to make the registration more anti-robot would be a lot easier than just having to report/delete threads all the time, and it would make the environment of the forum a lot more friendly to us humans.