The matter is that if you install spam protection from public sources, even if it is the last version, spam robots will soon start to process it because they are taught to process spam only in the case if it is installed in thousands of forums, because it is not reasonable to teach the program if it is installed only in one of the forums.
My idea of getting rid of spam and spam robots is like this:
if, when you register, you see a non-standard captcha, but a sigh like this "Enter the name of the forum where you waant to register" and and the field tor the answer, if you enter "PHPLIST" or "phplist", then you are allowed to register. Believe me, after that not a single robot will be able to register in your forum. I think that on PHP this engine can be quickly written.
