Buddypress / WordPress. Hackers Getting In……

I have been trying, (unsuccessfully), to post this on the Buddypress forum, and getting a error message, sooooo, here it is. Help please. ??

“I have been using bbpress and buddypress on my website as a test of usability. I have it ticked so that new users can create buddypress accounts, BUT, I must approve them before they become active. I have had a few hackers circumvent this, and create a buddypress user account, AND activate it. How are they doing this, and how do I stop it?”

Thanks for the buddypress answer AND if anyone can answer as to why I can’t post in the buddypress forum. I login, but it throws a error when I try to post.