UBB.Developers Forums UBB.classic V6.4 - 6.7 Modifications V6 Mod Ideas [REQ] Add CAPTCHA to Registration Form

Hello,
i'm using UBB 6.3.0.1
Each day i'm deleting about 30-50 spam messages on my board... is there a forumhack or smth else, that will add a feature "Image code check" during registration, that will prevent automatic registrations?
I search these forums about 3 hours... also surf all topics in section v6.0 - 6.3 mods, but only in this topic found a few words about captcha...