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Front Page » May 13, 2008 » Tech Tips » The Ubiquitous Captcha Serves As Hero in Disguise
Published 2,166 days ago

The Ubiquitous Captcha Serves As Hero in Disguise


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By JASON BAILEY
Sun Advocate/Emery County Progress


A modern CAPTCHA uses segmentation techniques to make the words readable by a human being, but difficult to interpret by opposing computer systems. CAPTCHAs are often used to prevent access to protected or sensitive websites from computer automation software.

The CAPTCHA is an interesting little thing. Despised by some and totally misunderstood by others, it is actually a hero in disguise.

The term "CAPTCHA" is a contrived acronym that stands for "Completely Automated Public Turing test to tell Computers and Humans Apart." The word was coined in the year 2000 by a team of individuals from Carnegie Mellon University and IBM, but the fundamental concept behind the CAPTCHA has been around since the 1950s.

The CAPTCHA is essentially a challenge-response test that attempts to determine whether the response was generated by a human or by a computer.

The test provides the respondent with a question that presumably only a human could answer. If the answer is correct, it is assumed the response was generated by a human being and not a computer.

So why should any of us care? Because most of us use them from time to time, whether we realize it or not. CAPTCHAs are frequently found online in a myriad of places, like message boards, banking sites, payment portals and even webmail sites.

The most common CAPTCHA displays a graphic containing letters or numbers. The characters in the graphic are purposely distorted to make the image harder for optical character recognition (OCR) software to interpret.

The respondent is asked to type the characters they see in the image into an adjacent text box. Once submitted back to the computer system, the CAPTCHA test is graded. If the correct answer is provided, the respondent is allowed to continue further.

While entertaining a CAPTCHA may seem like an unnecessary hassle, the fact is that they are often used to protect computer systems from neglect or misuse by bots and other malicious software programs that parade as something friendly.

For example, there are a host of text messaging websites that can send messages directly to a person's cell phone.

Suppose, for example, that someone decided to write a program that automated the process of filling out the website's text messaging form.

The software could be used to coerce the text messaging site into sending unsolicited junk messages to hundreds or even thousands of cell phones.

Without CAPTCHAs, the website would not know whether the messages were being sent by the program or by a real person.

But if a website adds a CAPTCHA to their website, it doesn't mean that it will stop abuse. Software has already been developed which can read and interpret many simple CAPTCHAs.

Graphically driven CAPTCHAs, for example, can often be bypassed by software with advanced optical character recognition software. So CAPTCHAs are always in a state of evolution to stay ahead of the game.

So, all in all, CAPTCHAs might be an annoying road block to deal with sometimes, but they're been brought to life to do good.

Have comments about this article or suggestions for a future Tech Tips article? Send an e-mail to webmaster@sunad.com.


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