Spam protecting the registration script

Would a secondary password protection for the registration page work?

Changing the name of the wp-registration.php file and password protecting this file solve spam registrations?

It appears that robot scripts are harvesting the registration file and once found a hack is used to run a script to register bogus usernames, email and passwords.

1) the obvious area is to stop more than one registrations from the same IP address
2) stop registrations from country IP address would help
3) from the user list spam is clearly visible just from the email address appear to be non personal.

The major issue is having to go through hundreds of email to mark as spam there must be a free alternative. Clean talk appears to charge for checking against their database.

WordPress needs to address this issue