Fake users registration attack

Hello everybody,

Since yesterday I have been under a spam attack. I disabled "Allow new users to register" option from Settings > Advanced Settings admin panel and I still have got attacks because new fake users have been registered.

Additionaly I have this plugins installed and enabled: uservalidationbyemail, recaptcha, iptracker, spam_login_filter, spam_throttle, honeypot and akismet.  

What can I do? Thank you very much.