Other subsite access & user listing

Hello,

Wondering if your plugin can restrict/deny access of users of one subsite to another?
Usually when a user (not superadmin) logs in to a network subsite, he’ll be able to access other subsites in the same network install.

Also, when buddypress is installed, they can list users of the entire network. Can you restrict them to list users only from the subsite they’re registered on?

Thanks