Well this technique is simple and will stop automated bots.. as always though if some one specifically targets your website on its own with specialized code you may still be in trouble.
It is quite simple to stop spammers on your website all you need to do is have a question on registration that is unique.. but eays for humans to understand it doesn’t have to be very complex at all just… how many words are there in….. that how simple it has to be however some spammers uses service with which the program collects registration questions and sends it to a person who answer them manually…… this does cost the spammers a little money each time however making a question that the person manually answering wont know will mean that spammers have no way to automatically get into your site and register……. a simpel question like what is our website name called? stopped my website from all spammers totally! The annoying thing though is that spammer use up the biggest part of your websites bandwidth!!!!!! and who get them there in the first place.. google……. spammers scrape google and even if your on the 20th page they will find and spam you google stupid they wont be giving you any real visitors only spammers unless you are on first page!