Most spam is human generated. That's why we're getting so much, it's almost impossible to filter without effecting genuine users. I know it's an extreme comparison, but that's why X is getting so much spam these days and are going to resort to...
Limiting newcomers to 1 thread and then setting a cool down won't fix the issues, simply because the spam is not being made by the same user.
What if @shaunj66 and @Costello makes a dummy forum that acts as a homepage or whichever forum gets...