First of all (for new users): simply do not post links in your first posts.
I found on several websites a great solution, which helps to stop spam bots.
Using captcha works to a certain limit, which seems to harden registration for people sometimes just as hard.
The solution which works pretty good thus far, is to ask people a 1 or 2 questions about a pictures and/or about something else.
The first could be something like a set of pictures, with a random question. Say an image of mobile (A)phone/(B)banana/©computer/(D)computer mouse/(E)Marge Simpson.
The question could be something like: Who knows Bart?
Or: Which can be eaten?
Or in text form question:
i.e. >The color of grass is; (green)
i.e. >1979 + 12 is for fun, just type here the result of 1 plus two; (3)
When these questions cna be randomised, or frequently updated,
it should be able to keep a lot of spambots away. Especially combined with a (simple) captha.
This could be used with every first X (15?) posts and every new registration.
I think at least…