CAPTCHA stands for Completely Automated Public Turing test to tell Computers and Humans Apart. Developed and trademarked by Carnegie Mellon University, the job of this test it to know if it's a person or a computer trying to access your system or website. Read more about CAPTCHA at http://www.protectwebform.com/.

After a CAPTCHA is installed, when there is an attempted access to the system there is a test given to determine if it is a human or a computer attempting access. Generally, CAPTCHA uses a picture of some distorted letters or numbers and asks for them to be retyped. A person can understand what the distorted letters are supposed to look like, while a computer cannot. Therefore, if the right answer is given, the test determines they are human. It's very easy to use and you can learn more about it at http://www.protectwebform.com/smartcaptcha.

Website owners have to guard against spammers yet they need feedback from the visitors to their site. Spammers are always on the look out to grab your email id and use it for various purposes without your permission. One option is that you can go in for automated programs, called bots, to let them scan your website and parse out your mail id.

CAPTCHA ensure that the spammers do not get access to your email ids. Many websites and sign up pages use CAPTHCA Plug-in (http://www.protectwebform.com/plugin_wordpress). The distorted messages that the user has to type in ensures that the user is human. CAPTCHA assumes that computer programs cannot read distorted characters.

As a fully automated program, CAPTCHA is so advanced it creates tests that can only be completed properly by humans. And since it runs itself, you don't have to baby-sit the system for it to work. This is why so many webmasters use CAPTCHA to keep their sites safe and secure.

CAPTCHAs prevent abuse of a system. Once spammers get access to your mail id, then you are trapped. You will be bombarded with spam mails and you can never be sure what your id will be used for.

In other words, CAPTCHA not only prevents encroachment by spammers for commercial purpose, it also protects the systems that are gullible to spam like, the webmail services of Gmail, Hotmail, and Yahoo. They also help prevent automated postings on online blogs. CAPTCHA helps in enforcing a usage policy and prevents any kind of deviation from the policy. This is required in case a service allows automated use but within a limit.

There have been numerous efforts at creating CAPTCHAs that are handier. Such endeavours usually include the use of JavaScript, mathematical questions (like "what is 1+1"), or simple questions requiring common sense (for instance "what color is the sky"). These attempts infringe on one or both of the philosophy of CAPTCHAs. Either they cannot be automatically created or they can be easily split given the condition of false intelligence. So, the only security these CAPTCHAs provide is safety through obscurity.