CAPTCHA stands for Completely Automated Public Turing test to tell Computers and Humans Apart. It is nothing but a program that helps you in knowing whether a user is a computer or human. It generates an image which has distorted letters and different pictures with different letters in different shapes. Finally it requests the user to enter the letters shown in the picture.
What Does CAPTCHA Offer?
CAPTCHA helps websites by protecting them from bots or better known as automated programs written in order to produce spam. It can only be read by humans and not computer generated programs. So it helps you in making your site secured and safe from bots. Bots are not capable enough to navigate sites that use it.
It is particularly important for sites that run free services. Take the example of Gmail or Yahoo Mail. You might have noticed sometimes that when you enter wrong password, you will find a CAPTCHA somewhere down and you cannot proceed further unless you enter the distorted texts or numbers. This is done to prevent abuses by automated programs.
Another major benefit provided by these is protection from dictionary attacks. Well, these are automatically generated scripts or computer programs which try random passwords where a login is required. Since automated programs cannot read these images; hence the login access is foiled.
CAPTCHA helps search engines to prevent crawling the spam contents that may be harmful for keeping database safe or sensitive data being exploited.
How CAPTCHA Can Be Created?
You can program a CAPTCHA using programming languages like PHP or ASP. However your code should meet three crucial requirements. First of all the code should generate a random picture with diverse properties. Next, it should validate the answer given by the user. And, lastly, it should make these pictures secure.
In order to make the code more reliable one can Rotate the text randomly, add random spaces in between characters, use a TTF fonts and change the font randomly every time, use a random text and image size every time, use more advanced text distortion and colors, move the lines randomly, store the password in a random cookie. Thus, using CAPTCHA in your application would help in making a trustworthy relation with your customers.