Internet companies working on new captchas

Microsoft researchers have developed an alternative captcha that asks Internet users to view nine images of household pets and then select just the cats or the dogs.

"For software, this is wildly hard," said John Douceur, a Microsoft researcher. "Computers are tripped up by all the photos at different angles, with variable lighting conditions and backgrounds and the animals in different positions."

The project, called Asirra (for Animal Species Image Recognition for Restricting Access), uses photographs of animals from Petfinder.com, a site that finds homes for homeless pets and has more than 2 million images in its database.

Other companies prefer to keep their next-generation captcha research quiet. Barrett of PayPal will say only that the new breed of captchas might resemble simple image identification puzzles, like asking users to view pictures of a head of lettuce, a tree and a whale--and pick out the vegetable.