For the past 2 days we've been getting hit with spammers on our forums. We have a security question that users have to answer when registering that a bot won't be able to answer because it's not a math question. So my guess is someone's bypassing it by either registering manually or something. They keep posting in one specific language (not english) and we ban their IPs manually. Any suggestions how to fight this? Anyone have any experience they can share and what they've done?