I have a multilanguage - multidomain website developed in Drupal 7, and the database have been flooded with spam comments, even if I have Captcha module (image) installed. The spam comments are from 60 different IPs, and I have seen attempts to add node and add user (which is blocked) in the incidents reports.
So I cannot block so many IPs at the risk of them being dynamical and loosing potential users.
What could I do to prevent the spam and also to prevent the attacks? Thanks