CAPTCHA's (Completely Automated Public Turing Test to Tell Computers and Humans Apart) are problematic, as they are often difficult for humans to read and relatively simple (with a little soft-hacking) for spammers to gain control. Fortunately, there is some innovation occuring in the CAPTCHA market, the latest of which is Captcha The Dog, a program that uses a random sequence of nine images (not letters or numbers) to foil spambots.
“Essentially it’s a game of ‘which one of these things is not like the other?’ A visitor must correctly select the one dissimilar image correctly 5 times in a row. The process is easy for humans, takes a few seconds, and is highly effective in deterring would-be spammers," said developer Daniel McMullan. “The key is that the site owner uses his or her own personal images.” McMullan says the images could be dogs and cats, trees and flowers, cars and trucks, trucks and flowers, or whatever the site owner chooses. He says that even when a human trains a spambot that is based on the site owner’s nine images, that spambot will only succeed once. “As soon as one spam gets through, a new image is integrated—that spambot now needs retraining.”
A free trial of McMullan’s CAPTCHA THE DOG application is currently available at: captchathedog.com. Users who want to deploy their own images, can set up a one-year customized CAPTCHA THE DOG account for $25.