Drupal 7 comments spam with Captcha installed 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
"to prevent the attacks" - not much can be done here. If an attempt to access node/add page ends with access denied page, its ok. You cant prevent users from entering urls in their browsers.

As for spam in comments, try some different modules for Captcha (Google reCaptcha with noCaptcha for example).
For different aproach, Honeypot can help limiting "robots" behavior.