CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) or HIP (Human Interactive Proof) are often used to reduce email and blog spam and prevent brute-force attacks on web site passwords. Microsoft has researched Asirra, a new Captcha with Pets.
Asirra (Animal Species Image Recognition for Restricting Access) is a HIP that works by asking users to identify photographs of cats and dogs; a task difficult for computers, but easy and accurate for humans.
Asirra has partnered with Petfinder, which provides over two million images of cats and dogs. Assira adds a small “Adopt Me!” link beneath each photo, supporting Petfinder’s primary mission of finding homes for homeless animals.
Check out examples of Asirra at work in which you click on all the images that show cats. Learn how to set up Assira on your site and stop spam.