Random image text generation?

[Paul Rubin]

Steven D'Aprano <steve at REMOVE.THIS.cybersource.com.au> writes:
> Instead of displaying an obfuscated image of a nonsense word, display six
> randomly chosen photos, where five are of the same thing but not the same
> image. E.g. you might show five different kittens and a horse. The user
> has to click on the image that is not the same as the others.
> State-of-the-art horse-recognition software is not yet in widespread use
> by spammers *wink*

No need to recognize the horse.  Just pick one of the pictures at
random and you'll get the right one 1/6th of the time.  Repeat ad
infinitum--they're spammers and like to repeat stuff after all.
That's why those conventional captcha images make you recognize a
multi-character string: so the guessing chance is low.