Spam

I recently set up BuddyPress on my site and have already had about 15 people sign up. I believe this is spam because my site has no information on it for anyone to read and even know what they are signing up for.
I'm wondering if there is a plugin or something I can install to stop the spam from coming in.
Also, those that have already signed up is there a way to tell if it is spam or not?

Thanks