Asirra

[KillerDotNet]

Asirra

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.

HIP Example 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 to identify photographs of cats and
dogs. This task is difficult for computers, but our user studies have
shown that people can accomplish it quickly and accurately. Many even
think it's fun!

Past projects have used photographs to tell computers and humans
apart. Examples include Carnegie Mellon's PIX CAPTCHA, Oli Warner's
KittenAuth, and work done by Chew and Tygar. These projects have a
common weakness: they use relatively small image databases. There's a
fundamental reason for this. It's difficult for a computer to
automatically classify pictures with high accuracy — that's why the
task is useful as a HIP. An image database small enough to be
constructed manually by a researcher is also small enough to be
manually reconstructed by an attacker.

Asirra is different because of our unique partnership with
Petfinder.com, the world's largest site devoted to finding homes for
homeless pets. They've provided us with over three million images of
cats and dogs, manually classified by people at thousands of animal
shelters across the United States. In exchange, we provide a small
"Adopt Me!" link beneath each photo, supporting Petfinder's primary
mission of finding homes for homeless animals.

Our work was inspired in part by Frozen Bear's HotCaptcha, which
similarly uses a large database of manually classified images as the
basis for a HIP. We were motivated to improve on the idea because
HotCaptcha isn't really appropriate for widespread deployment. Asking
users to rate people's attractiveness is potentially offensive, and
the challenge does not have any ground truth.

http://research.microsoft.com/asirra/