Deinitely need to use multiple methods that create a weighting system to assist with filtering. The Referrer method, coupled with the javascript payload that Declan mentioned, and a keyword filter are probably the quickest/least painful combination to stop the vast majority of spam. But that negative Captcha sounds very intriguing.
Deinitely need to use multiple methods that create a weighting system to assist with filtering. The Referrer method, coupled with the javascript payload that Declan mentioned, and a keyword filter are probably the quickest/least painful combination to stop the vast majority of spam. But that negative Captcha sounds very intriguing.