phpbb captcha system

The-Master

I just decided to make it like php.net bot stopper system. It wouldn't be that secure if it was used a lot but this is the only forum that uses my system and the chances of a custom bot being built is slim.

Anyway check it out.

Click register and confirm you are old enough and then see the new system for bot stopping.

Feedback & constructive criticism welcome.

Piranha

It is looking good. But I have a few ideas how you could change it.

Remove "" in the source. This would probably be information that a bot could use.
Don't use the name "confirm_code", it is to easy to find. Instead use "email_confirm" or something else that doesn't have to do with confirmation.
Include the normal captcha from phpBB, but hide it in the css. This will fool most bots that you actually use that captcha.
Don't just use add. Use subtract, multiply and divide as well.
Place the text in a picture. Or not, there are advantages and disadvantages for both ways. Don't place it in a picture if you include the normal captcha.
Use big letters, small letters and numbers as well as both symbols and words for add, subtract, multiply and divide. With a picture like "TWo adD 33" or "foUR - ThREe" it will be harder for a bot to understand that it is not just a normal picture captcha.
Later on it could be a good idea to include other type of questions as well. Colors are one way (don't use the color name in the code, use the code for the color) "what color is this text?" Questions that you have to understand what it says to be able to reply is also good, like "If Adam have six apples and give Eva two, how many apples do Adam have left?". It is just mathematics when you and I read them, but a computer won't understand it that easy.

The-Master

Thanks for all that help. I will try and implement some of it at some point but some of the ones that make it more complicated for the user like number 6 I am trying to avoid because I still want it to be reasonably easy to complete. I will modify it if bots start to sign up but I doubt that will happen.

Thanks!