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What is CAPTCHA? Technology Explained!

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What is a Captcha and how is it used?

CAPTCHA or Completely Automated Public Turing test to Tell Computers and Humans Apart is a technique to distinguish between humans and computers. CAPTCHA is mainly used as a security check to ensure only human users can pass through. Generally, computers or bots are not capable of solving a captcha.

What is the purpose of Captcha?

The technology is used mostly to block spammers and bots that try to automatically harvest email addresses or try to automatically sign up for or make use of Web sites, blogs or forums. CAPTCHA, whose users include Yahoo and Google, blocks automated systems, which can’t read the distorted letters in the graphic.


CAPTCHA Explained!! —

If you’ve ever tried to register with a website or comment on a blog and been asked to enter some crazy characters that have been all jumbled up, you know how frustrating it can sometimes be to tell a lower case L from a number 1 or an uppercase O from a number 0.

Those crazy codes are called CAPTCHA and they are a human response test. The word is actually an acronym for: Completely Automated Public Turing test to tell Computers and Humans Apart.

How Does a CAPTCHA Work?

The reasoning behind why websites implement CAPTCHA codes into their registration processes is because of Spam.Those crazy letters are a way to check if the person registering or trying to comment is a real live human being as opposed to a computer program attempting to spam the site. Yes, it’s the same reason most of us have some form of spam blocker on our email.

CAPTCHAs were invented to block spammy software from posting comments on pages or purchasing excess items at once. The most common form of CAPTCHA is an image with several distorted letters. It is also common to choose from a variety of images where you need to select a common theme.

Spam is the modern day equivalent of junk mail. But, if the spammers were in charge, the junk mail wouldn’t just be in your mailbox or tied to your doorknob. It would litter your yard, bury the car parked in your driveway, plaster every side of your house, and cover your roof.

The internet and computers are actually made up of a unique coding language. Computers find it difficult to understand languages because of the strange and intricate rules human languages take on, along with slang that humans use.


CAPTCHA is used on a variety of websites that want to verify that the user is not a robot. First and foremost, CAPTCHA is used for verifying online polls. In 1999, Slashdot created a poll that asked visitors to choose the graduate school that had the best program for computer science. Students from the universities Carnegie Mellon and MIT created bots, or automated programs to repeatedly vote for their schools.

These schools received thousands of votes, while other schools only hit a few hundred. CAPTCHA came into play so that users could not take advantage of the polling system.

If a site or blog owner didn’t use some type of protection like CAPTCHA against it, they would be getting dozens of spam registrants or comments a day. And that’s just for small websites and personal blog that aren’t very popular. You can only imagine what the popular blogs must see.

So, next time you run up against one of those images and get a little frustrated trying to tell a Q from an O, just remember not to vent your frustration at the website. Focus it on the spammers, because they are the reason we have to squint at our screen almost every time we want to register at a new website.

Another use of CAPTCHA is for registration forms on websites such as Yahoo! Mail or Gmail where people can create free accounts. CAPTCHAs prevent spammers from using bots to create a plethora of spam email accounts.

Ticket websites such as TicketMaster also use CAPTCHA to prevent ticket scalpers from over purchasing tickets for large events. This allows legitimate customers to purchase tickets fairly and keeps scalpers from placing thousands of ticket orders.

Lastly, web pages or blogs that contain message boards or contact forms use CAPTCHA to prevent spammy messages or comments. It does not prevent against cyberbullying, but does prevent bots from posting messages automatically.

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