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After harping all week on tough problems in business ethics, I thought I’d wrap up today talking a rather neat design idea from Google.

Screening out automated computer systems (from, e.g. signing up for e-mail accounts or posting spam comments) is an ongoing problem on the Internet. Many of us already know about the popular CAPTCHA (completely automated public Turing test to tell computers and humans apart) technique, which traditionally uses noisy text readable to humans but not to bots.

Recognizing that there are a variety of good reasons to think about a new style of Captcha, Google has designed a novel Captcha strategy that employs images that are easy for people to orient correctly, but hard for computers.

From the paper, What’s Up CAPTCHA?:

Image credit: Google

This task requires analysis of the often complex contents of an image, a task which humans usually perform well and machines generally do not.

Given a large repository of images, such as those from a web search result, we use a suite of automated orientation detectors to prune those images that can be automatically set upright easily. We then apply a social feedback mechanism to verify that the remaining images have a human-recognizable upright orientation.

The main advantages of our Captcha technique over the traditional text recognition techniques are that it is language-independent, does not require text-entry (e.g. for a mobile device), and employs another domain for Captcha generation beyond character obfuscation. This Captcha lends itself to rapid implementation and has an almost limitless supply of images.

We conducted extensive experiments to measure the viability of this technique…Our Captcha technique achieves high success rates for humans and low success rates for bots, does not require text entry, and is more enjoyable for the user than text-based Captcha.

Nice.