Re: Captcha and Spam blocking

[tnash]

Ultimately what ever you do is an up hill struggle, using CSS to stop Spam bots is not a bright move, and of course would be an accessibility nightmare (as are visual only Captchas) and potentially if your in the EU and a commercial outfit might find a kind lawyer chasing you for money.

The second issue is known captchas can be broken, for example the CAPTCHA being used on this forum has already been broken and therefore is really useless. Also the lack of audio version would again raise the accessibility issue again, when designing and thinking about CAPTCHA you might be interested in the 10 steps to solve a CAPTCHA by Dark SEO (he also has a post on PHPBB3 captcha by the way).

I prefer logic puzzles, for example a simple version is to present a maths puzzle, one + 3 equals or 4 plus 1 = notice the changing from words to symbols, throw in some French or odd variances. A good example I saw was the human only maths by using human derived groups to do the maths so:
There are 5 tigers and three lions and two wolves how many animals are in the cat family?

Because the question is done server side it will be rendered in any browser without accessibility issues. These can of course be broken but by personalising the questions and groups a spammer will have to write a program specific fo your site.

One other alternative used by companies like StumbleUpon and FaceBook is recaptch which is an attempt to digitalise old books, this is also much harder for computers to break as at least one part is unsolvable (or rather it has no answer) for more information check out http://recaptcha.net/