You can enable moderation for moderating new BuddyPress members and fight spam bots. BuddyPress Registration Options is a free WordPress plugin that allows you to do so. Simply install and activate it. After activation you can manage all its options and features from its admin section.
If moderation is on then any new members will be kept blocked from interacting and using any BP elements except editing their own profile and avatars.
Even they will not be listed in any member’s directory until their accounts get approved by the administrators.
When moderation is on, admins can create custom display notice messages and email alerts for approved or denied user accounts to tell them they were approved or their request is denied.