Fake members

[ukmma]

Is there a mod that can be installed to stop or slow down the registering of fake members, my forum has hit the top of google for some specific keywords increasing site traffic quite a bit, but ive gone from 3 or 4 fake members signing up a day to 15+ and its getting anoying deleting them all, i just dont want them showing up on my site some of them spam the forum some dont post at all, but when they have usrnames such as xchdyun and allenidhu its quite obvious they are fake members, so if anyone knows of any mods that can be installed or settings that can be changed in my cp please let me know

Thanks