Stop auto-registration when spam-controls enabled?

[Fusion2]

I accidentally enabled my website this morning. Up until now, registration was disabled, while i continue modifying site design.

Within 2-hours, I got 36 registered users, and it looks like all of them are spam-related.

Not sure how they registered so quickly, as i have email confirmation, Unique Email, Dont allow Multiple Registrations, and have GD enabled. I also have several custom profile fields that require imput, such as date of birth, location etc.

These spammers not only did the full registration, but also added homepage and signature information to their profiles.

I was so concerned that I modified my usergroup 2 (members) to restrict a lot of what members can do, and to make this usergroup a moderated default. Then when they can be trusted, i will move them to a less moderated usergroup.

How can I improve my registration process, and void spam?