One character is the whole attack
Checked, not guessed
A name is called registered only after the answer is confirmed against the registry that holds it. A single wrong answer never reaches you as an alert.
Ranked by what it can do
A name registered days ago that can send mail ranks above a name that has been parked for ten years. You read the dangerous ones first, and the reasons are named on each one.
Your own names stay safe
A block request never goes out against a name that the service reads as yours. The check runs before a person can approve a request.