From what I've seen they've found their way around Captcha and other "bot proof" technologies by paying people a menial fee to manually post.
No, I think the bot software has gotten so good that it can read and decipher captchas. That is why captchas are getting harder and harder for humans to decipher. I hate the damn things.
I don't see how they get by the requirement for new users to receive a confirmation email. It must be a hole in the old software we are running.
I think the spam would be reduced considerably if new users had to be confirmed by a human admin before they could post. On the other hand, that could add a fair workload for the admins. Perhaps new users could be restricted (for posting) to a sub-forum just for the purpose of introducing themselves and asking for general posting privileges? Of course, that sub-forum could fill up with the same spam...
We might give delete privileges to all users in that board only.
I also like the idea of requiring 5 response postings before being able to start a new thread. It's my impression the large majority of spams are new threads.
To do any of these things, or upgrading software which is the correct first step, requires an admin who is around. We don't have that. IIRC I once volunteered to take that over with the proviso I could get some help from Joseph as a backup when I couldn't figure things out, but that went nowhere.