Unfortunately there is no universal way to stop forum spam. There are programs like All Submitter and Xrumer for automated submissions, and they can resolve simple captcha protection. For more complicated text modification (such as reCaptcha) there are services for spammers, where hundreds of people sit and recognize captcha for as low as $1 per 1000 captcha codes! It is hard to believe, but it is true. This is a black/gray SEO, and it’s a huge industry.
Blocking IP is a good solution to protect your forum from newbie spammers. But mature spammer will proxy servers! A lot of proxies. There are thousands of free proxies available, and there are services where you can rent proxy ID for small fee.
Ask yourself what attract spammers to your website? Ability to post their LINKS! They fight to place their backlinks on your forum, even for a very short time (they know their profile will be banned and all the posts deleted). Search engines like popular forums and their crawlers index new posts on such forums very fast, so if you delete spam post in a hour after it was posted, the chances are that this post is already indexed by googlebot - that’s enough for spammers. They will return to your site again and again.
If your forum have high google PR, and/or have a large and loyal audience - you need to pay much attention to any links (both in profiles and posts), and to any suspicious posts. Say if someone has registered on your forum just to say:
Hello[url=http://www.phphelp.com/forum/index.php/board,12.0.html],[/url] what a great website! [url=http://www.phphelp.com]:)[/url]
don't let them fool you - check if there is a link behind the SMILE icon, or a link behind point/exclamation/comma etc. (I actually posted links in the example above, to demonstrate how you can miss this). You may think this is not a big deal - people do not see these link, but Search Engines DO! And that's make your forum a target for Spam.
Here are several tips how to stop forum spam and make your website less attractive for spammers.
You may or may not find a corresponding mod/plugin to implement these features on your forum script, or hire php programmer to make customization to your forum script.
[ul][li]Use reCaptcha or other human verification procedure on new member registrations or guest’s posts[/li]
[li]Disallow indexing forum memberlist by search engines (you can do this by adding rel=“nofollow” attribute in the script code, or by adding directives to robots.txt)[/li]
[li]Set permissions to allow posting URLs only after NN days from user registration, and/or after they have XX posts (this will make your website less user friendly, but less attractive to spammers too)[/li]
[li]Disallow links in forum signature for new members (again, make it available only after user have XX posts, and/or NN days since their registration on the forum[/li]
[li]Disallow editing posts for new members and limit post edit time for any other member (some clever spammers will return to edit their old posts to insert links)[/li]
[li]Use stop words list to censor repeating spam posts (since spammers use an automated posting software, sometimes stop words list help to filter a lot of spam posts promoting the same service/product/website)[/li][/ul]
Hope this helps.
