"Tony" <tony@ttiger.co.uk>
[...] The majority are from bots and most now can crack a Captcha. What has proved to be most effective is having a simple questions and answer, I just have four that randomly rotate on each sign up. Haven't had a single spam sign up since I done it.
When they crack that, http://textcaptcha.com/ is probably the next step. Trouble is, any sufficiently popular site will also attract human spammers, so you also need some anti-spam measures, like not letting people post links just because they've signed up (like: no homepage link in the profile until after they've made N links). As well as most of them being fairly crackable automatically, image and sound captchas also block users with even fairly minor disabilities, so I think they probably make one fall foul of the Equality Act 2010, but I also think we're still waiting for case law. Good luck! -- MJ Ray (slef), member of www.software.coop, a for-more-than-profit co-op. Webmaster, Debian Developer, Past Koha RM, statistician, former lecturer. In My Opinion Only: see http://mjr.towers.org.uk/email.html Available for hire for various work through http://www.software.coop/