Block spammers and crackers from your Rails app
If you want to cut down on the nastier elements getting through to your Web site, filling in contact forms, and generally causing havoc, consider the rbl_check plugin by Joost.
rbl_check is a Rails plugin that checks every incoming request to see if the client is listed on a Real-time Blackhole List. This helps prevent abuse from spammers/crackers.
Basic source for implementing a block is included.