Hacking For Beginners – Manthan Desai
Who Uses CAPTCHA?
2010
CAPTCHAs are mainly used by websites that offer services like online polls and registration forms. For example, Web-based email services like Gmail, Yahoo and Hotmail offer free email accounts for their users. However upon each sign-upprocess, CAPTCHAs are used to prevent spammers from using a bot to generate hundreds of spam mail accounts.
Designing a CAPTCHA System
CAPTCHAs are designed on the fact that computers lack the ability that human beings have when it comes to processingvisual data. It is more easily possible for humans to look at an image and pick out the patterns than a computer. This isbecause computers lack the real intelligence that humans have by default. CAPTCHAs are implemented by presentingusers with an image which contains distorted or randomly stretched characters which only humans should be able toidentify. Sometimes characters are striked out or presented with a noisy background to make it even harder forcomputers to figure out the patterns.
Most, but not all, CAPTCHAs rely on a visual test. Some Websites implement a totally different CAPTCHA system to tellhumans and computers apart. For example, a user is presented with 4 images in which 3 contains of animals andone contain a flower. The user is asked to select only those images which contain animals in them. This Turing test caneasily be solved by any human, but almost impossible for a computer.
Breaking the CAPTCHA
The challenge in breaking the CAPTCHA lies in real hard task of teaching computer how to process information in a way
similar to how humans think. Algorithms with artificial intelligence (AI) will be designed in order to make the
computer think like humans when it comes to recognizing the images. However there is no universal algorithm
that could pass through and break any CAPTCHA system and hence CAPTCHA algorithm must have to be tackled
individually. It might not work 100 percent of the time, but it can often enough to be worthwhile to spammers.
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