Yeah the problem is that the forum software is 8 years old. and the current generation of spambots are either reading the page code for the authorisation code or just using ocr to replicate it.
So in the process of updating.
I'm half way there.
the procedure for either modding or updating the forum software (what I'd prefer) is three fold:
1) download an exact copy of the forum to my computer - took 2 days but I'm pretty sure I've done that bit. Which gives me a working copy.
2) modify the foum while it's on my computer and then perform as many checks as I can to make sure it all works.
3) shutdown the forum and upload the modified sections back to the server.
4) pray it works
Currently got a lot of actual work on so it'll be a few days or a week or so.
Worst case scenario I can always stick the old software back on.
But it's going to happen
If I can I'll update to yabb 2.5 which has a lot of the security mods already installed as well as a bunch of other stuff that would be good.