I've developed an alternative to captcha for blog comment/forum spam a while ago. There are many methods that are easily dismissed with "but not all spam is li

I've developed an alternative to captcha for blog comment/forum spam a while ago. There are many methods that are easily dismissed with "but not all spam is like that" and "someone could work around it easily": • blocking of links (if you don't need them, or in fields that are not for them). • blocking of obviously spammy keywords (or bayesian filter) • invisible fields and syntax to trip up dumb implementations • requiring JS, properly-functioning cookies • blocking of IP ranges that belong to VPS providers and a couple of 3rd world telecoms that allow spam Each of them is surprisingly effective and combined they block 99.8%. You really shouldn't flatter yourself thinking that a spammer will even look at your page. They have literally millions of sites to spam, and they couldn't care less if they get yours or not. A bot will find a 1000 other sites to spam quicker than it takes a human to click "View Source". Most of spam is done by amateurs who take shitty off-the-shelf spam software, seed it with a target list copied off some forum, and run it on a couple of spam-friendly or incompetent VPS hosts. By volume, this is the vast majority and it's very easy to block.