Hopefully the Administrators are already using these to help defeat the spammers:
1. Make sure links in your forum are set to ‘nofollow’. This tells search engine crawlers not to follow the links and therfore, SEO spammers will derive no benefit from spamming your forum.
2. Make sure registration includes a CAPTCHA. Captcha’s are those slightly deformed images of words and you see on sign up pages. Captcha’s do a pretty good job of keeping out spam bots.
3. Require email confirmation before allowing someone to post. Bots and humans can get around this but it's an extra bit of efforts that most real people won't mind.
4. Enable anti-spam plugins. These plugins can automatically detect suspected spam based on links, IP addresses, email addresses and the comment itself. Keep in mind that these plugins are not 100% effective and do sometimes return false positives.
5. BLOCK CHINA!!!!! Virtually all forum spam (and blog comment spam) originates in:
More than a third of all forum spam comes from China!
Unless your site targets people from the part of the world, there’s no need to cater to them. You can safely block them from participating on your site. They can still see and read the site — they just cannot comment or post. (And in the atypical case that you get that one person that is an asset to your site — but simply happens to live in an area of the world surrounded by spammers — you can always manually create an account.)
Think about it: you can reduce at least 33% of your spam by blocking China alone.
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