Oh, this is a much better way of testing whether someone is human when they visit a website. Most sites, annoyingly, ask users to decipher some distorted letters on a screen, and type them into box. I get it wrong, often enough. Enter Microsoft Research. Redmond's boffins have exploited the very human ability to tell apart household pets. The Asirra system — designed to thwart spammers who use software robots to hack into systems — asks users to look at an array of a dozen randomly selected images of cats and dogs, and identify the felines. The service is available, for free, to web site owners. Finally, a Microsoft Research project that's actually useful.
