CAPTCHA (Completely Automated Public Turing Test To Tell Computers and Humans Apart) is a programme used by many blogs and websites to help prevent fraud and spamming. It produces a test that a human can pass but a computer programme (so far) cannot.
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In 2000, four computer scientists from Carnegie Mellon University, Luis von Ahn, Manuel Blum, Nicholas Hopper and John Langford, created the very first CAPTCHA. This was used by Yahoo to prevent computers opening email accounts. According to Carnegie Mellon University, around 200 million Internet transactions are protected by CAPTCHA every day.
CAPTCHA improves online security in many different ways. It is often used to prevent spam in blogs, as only humans are able to leave comments. Another use is in online polls, to ensure only humans are voting and the results of the poll can be trusted. The application can also be used to keep webpages unindexed by blocking search engine bots from reading them. To stop hacking in password-protected webpages, CAPTCHA can be used after a specific number of failed attempts.
CAPTCHA and Gmail
To stop automated computer programmes signing up for thousands of free email accounts at a time, companies such as Google, Yahoo and Microsoft use CAPTCHA to make sure only humans can set up free accounts. When signing up for a Gmail account, after you have entered your personal details, you are asked to "prove you are not a robot" by solving a CAPTCHA before you can move onto the next step.
Problems with CAPTCHA
If you are experiencing difficulties accessing Gmail or receiving an error message when you try to log in, you may need to reset CAPTCHA. After making sure you are using the correct username and password, go to the Display Unlock CAPTCHA page on Google (see Resources). Entering your email address and password in the correct boxes, typing the CAPTCHA characters shown on the screen in the box provided and clicking "Unlock" should take you directly to your Gmail account.
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