How do I protect my forum against spam?

Question

I have a forum on a website I master, which gets a daily dose of pron spam. Currently I delete the spam and block the IP. But this does not work very well. The list of block

Answer 1

Advanced solutions:

• Akismet
• Defensio
• Sblam! (open source clone of the above)

You can try your luck with non-standard form:

• fields that must stay empty hidden with CSS
• fields with misleading names, e.g. <input name=email> for something that is not an e-mail.

For me CAPTCHA is like giving up to spammers and letting them damage your forum anyway – except that instead of spam damage, you get usability and accessibility damage.

Answer 2

Captcha is definitely the easiest method - try KittenAuth if you want something bot-proof (Although I got pandas this time)

• Kitten Auth

Answer 3

There is no single answer since Spam is really a matter of economics: how much is it worth it to someone to put their stuff onto the web. There, however, some solutions that seem pretty good

• Recaptcha
• Use CCS to create an invisible field that robots fill-in
• Create a time-specific hidden field in your form so the robot can't use the same form over and over again.

Answer 4

One way that I know which works is to use JavaScript before submitting the form. For example, to change the method from GET to POST. ;) Spambots are lousy at executing JavaScript. Of course, this also means that non-Javascript people will not be able to use your site... if you care about them that is. ;) (Note: I don't)

Answer 5

Something I've found to be surprisingly effective: disallow comments that contain too many URLs (more than, say, 5). Since doing that, I've had zero comment spam.

Edit: Since writing the above, I've had recurring comment spam with only one link. I have now added some honeypot fields and have had no commend spam for a few months now.

Answer 6

You could use a captcha, there are some good scripts like PHPCaptcha or use a spam control service, like Akismet, they have a PHP API.