Instiki
Anti Spam

Current Anti Spam techniques planned for patches and a instiki anti-spam edition 0.12

• dnsbl_check included in instiki
• creating a tarpit-wiki (see Ruse-Anti Spam Measures)
• creating captchas graphically—searching for a pure ruby imaging solution such as Perl’s Imager which is not dependant on libraries like imagemagick (see reCAPTCHA or rubyforge project CAPTCHA)
• captchas in ascii see lemming.name or tppcaptcha
• SIMPLE hidden fields create hidden fields to see if posted by bot or by human (like clearthisfield)
• Have you thought about using Akismet ? Rails-Akismet Howto
  . I think it should also work with Ruby-only apps.

see also how the guys at mediawiki do it
http://meta.wikimedia.org/wiki/Anti-spam_Features
and of course the wiki.rubyonrails discussion about spam
http://wiki.rubyonrails.com/rails/pages/HelpFightSpam