AntiSpam measures on websites

Question

What are anti-spam measure i should consider before launching my user content website? Somethings i have considered

• Silent JavaScript based captcha on the register page (i do not have an implementation)
• Validate emails by forcing a confirmation link/number
• Allow X amount of comments per 10mins and Y per 2hours (i am considering excited first time users who want to experience the site)
• Disallow link until user is trusted (i am not sure how a user will become trusted)
• Run all comments, messages, etc through a spam filter.
• Check to see if messages are duplicate or similar (i may not bother with this. I'd like the system to be strong without this)
• I also timestamp everything which i then can retrieve as a long on my admin page. What other measures can i take or consider?

Answer 1

Have a flag option like stackoverflow. :-)

Answer 2

You should probably implement some means to track and if necessary block IP addresses or ranges from posting to your site.

Also, as I recently saw on an image hosting site, you could randomly pop up a CAPTCHA every so often to verify humanity.

Answer 3

Django has some anti-spam measures that you could implement in your language of choice - so-called "honeypots" (form fields which you hide with CSS, which bots might fill in - if the field is filled in guess that it's a spam entry), timestamps etc - see the Django documentation.