How CAPTCHA Works

• A CAPTCHA can come in several forms, but the general idea is that it administers a test that only a human could pass. The CAPTCHA program usually shows a series of letters or numbers that aren't in a traditional format that can be read by computers. You're then asked to enter the information in the image. The program will then check the answer you provide to make sure that it's correct.
  
  

CAPTCHA Basics

• Staff members at Carnegie Mellon University developed Completely Automated Public Turing Test To Tell Computers and Humans Apart as a way to help Yahoo! keep automated bots out of chat rooms. These bots were attempting to send users to advertising sites and make money through the chat rooms. With the help of CAPTCHA, Yahoo! was able to reduce this problem. This program typically uses distorted text images to provide information to you. You must interpret this image and the CAPTCHA program will grade the answers. If the correct answers aren't given, you can be denied access to certain areas of websites.
  
  

Protect Registrations

• One of the primary uses of the CAPTCHA program is that it helps companies protect registrations. Many scam artists attempt to use automated programs to sign up for accounts such as email and social networking accounts. By requiring new registrants to enter a CAPTCHA code, the services can protect their interests. This helps keep automated accounts from being created and forces people to sign up without the help of a computer program.
  
  

Avoiding Spam

• The CAPTCHA program is also commonly used to help protect websites from being spammed. For example, the comments section of a blog is a common target for this type of activity. People trying to promote a product might fill the blog comments with links to products. By requiring a CAPTCHA code, the blog can prevent people from spamming the comments. This is also used with other sites to prevent spammers from being able to generate a large amount of promotional spam.