I suggest you guys turn on in cpanel, "do not allow posting in the forum to unverified signups". |
Also try to use a series of well thought out tricky questions and answers, with no questions like whats 2+2 with numbers, rather more like whats two plus two - spell the answer-no numbers, on sign up.
Find a good spam bot plugin.
This can help cut down on annoying spam bot problems. Peace!
How To Stop phpBB3 Registration Spam Bots