Google Tried New Captcha Method
Technology.am (Apr.20 , 2009) — Google, which already devoted a lot of resources to block e-mail and Web spam, has tried a new test to keep the bots at bay.
Google authors have described the image-orientation technique. This task requires analysis of the often complex contents of an image, a task which humans usually perform well and machines generally do not.
A large repository of images are given from a web search result, we use suitable automated orientation detectors to prune those images that can be automatically set upright easily. We then use a social feedback mechanism to assert that the remaining images have a human-recognizable upright orientation.
The test is the latest variation on a screening technique called a Captcha (completely automated public Turing test to tell computers and humans apart). The idea is that people can often tell which way is up in a photo, but computers have a harder time.
The main advantages of the Captcha technique over the traditional text recognition techniques are that it is language-independent, does not require text-entry, 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.
I hope there’s going to be a NSFW version of this captcha. Can’t wait for people getting it intentionally wrong to see ANOTHER ONE, heh.
And, of course, there’s no chance at all that the bots would simply pick an image at random. Why, a website could have 10 images, and the bots would only get through 10% of the time. That sort of success rate would clearly make the spammers pack up and go home.
A site with 10 images per captcha would be guessed 1 in 1024 times, not 1 in 10.
Do a google search for e.g. “dog” and look at how many are upright. Almost all. That means that a computer could generate captcha’s using huge amounts of web data and most spambots would never see the same image twice.
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