Standard confluence captcha is compromised. How to use different captcha for Spam Prevention?

[Max Pavlov]

Hello. Confluence ships with an embedded Spam Prevention mechanism that enables admins to turn on captcha for comments on an open wiki, so when an anonymous user wants to post a comment, it must validate that it's not a bot via entering a captcha.

Even with captcha enabled we are getting a ton of Spam comments on our indexed pages. I suppose spam bots are having an easy time going through the standard captcha that Atlassian currently ships with Confluence. 

Is there a way, a plugin perhaps, that allows using a different captcha implementation on comments?

[jriley-es]

I am looking to migrate a Knowledgebase into Confluence and we would like to have anonymous comments, if possible.

As OP asks, can we get a different Captcha? or Captcha API?

Can we get Comment moderation?

Stronger Captcha? or a configurable challenge/turing test question?

[AnnWorley]

I did not find an add-on that will apply a different captcha for anonymous comments.

As Nic points out in captcha bypassaed, the captcha mechanism in general is not the most bullet-proof.

Have you considered disabling anonymous comments or is that functionality necessary for your instance?