I heard that user registration is disabled on
www.Amigans.net, due to spam bots. Is this true?
If yes, then I guess a normal CAPTCHA wasn't working? I have some alternative suggestions, based upon what I have read websites using:
Since spam bots tend to fill *all* Form fields, put one or more hidden fields, and then reject forms which have data in those fields!
Rather than (only) image-based CAPTCHA, what about adding some simple questions in English? While they could be universal things like "What is four times three?" or "Type the contents of the box above", you could make it more difficult for bots by having topical questions like "What is the name of this website?" (would require allowing several possible answers) or "Which computer is this website for? (5 letters, begins with A)" or "Which company originally sold the Amiga? (begins with C)" or "Which company has the C= logo?" etc. This would also make it tricky/impossible for people unknowingly being made to solve *your* CAPTCHA on some other website (say a porn site secretly selling it's users services for extra cash).
You might also want to put time-limits on CAPTCHA, to help thwart bots which send your CAPTCHA question to some other website for solving.
I don't think any single solution will solve the spam problem, but a combination of solutions (none of which would have to be tricky for legitimate users) when combined would dramatically cut the volume of spam registrations that get through (possibly even to zero).