A couple of thoughts about trapping comment spam: my first idea was, add a textfield requiring a significant word from the blog entry in question. Simple for a person to produce, and in practise you just need to check if the word occurred in the entry at all, skipping a list of obvious stop words (“in”, “the”, etc.).

But of course a clever robot spider from hell can deal with that: the same technique generates magic words as tests for them.

So my second idea was a textfield already containing a word, with a note saying “If you submit this form without clearing this textfield, I’ll know you’re a robot spider from hell.” Better still, “Change this word to the one following it in the article above, to prove you’re not …” You get the idea.

For added fun, rotate these methods (and the simpler “Don’t fill in this textfield unless you’re a RSfH” on eg. the URL field) at random. If I didn’t have a thesis to write, I’d put together a wordpress plugin.

(Why am I thinking about this, given the obvious lack of comment spam on my blog? Because (a) I still occasionally moderate down posts advertising the-card-game-whose-name-we-do-not-speak, and (b) I’m terrified that one of the extremely infrequent genuine comments of my friends is going to get blitzed. It’s not that I don’t trust Spam Karma, it’s simply that I don’t understand it.)