Asirra is a human interactive proof that asks users to identify photos of cats and dogs. It's powered by over three million photos from our unique partnership with Petfinder.com . Protect your web site with Asirra — free! Overview Web services are often protected with a challenge that's supposed to be easy for people to solve, but difficult for computers. Such a challenge is often called a CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) or HIP (Human Interactive Proof). HIPs are used for many purposes, such as to reduce email and blog spam and prevent brute-force attacks on web site passwords. Today, the most common HIPs ask users to identify text that has been distorted or obscured, like the example seen to the right. Unfortunately, such challenges can be difficult and frustrating for people, yet are often easily solved by computers. Asirra (Animal Species Image Recognition for Restricting Access) is a HIP that works by asking users...