CAPTCHA , Completely Automated Public Turing test to tell Computers and Humans Apart, is a web security technique to protect HTML forms from web spammers. CAPTCHA dynamically generates security codes for sign-up, subscription submission or checkout forms to make sure that forms are not submitted by spam bots.
Because the generated password on a distorted image is a part of the image, users can’t copy and paste it. This way, it verifies that it’s an actual human that submits a form, not any kind of automated software including spambots.
The security codes that CAPTCHA generates are usually a combination of letters or digits that doesn’t mean anything. This technology can be used for any form submission on the Internet, including user registration, e-commerce transactions, surveys, Internet polls, search engine submissions, or free email registration.
Free CAPTCHA installation plug-ins are available for many environments or languages including PHP, Perl, Phthon, WordPress, or MediaWiki.
Advantages of using CAPTCHA from captcha.net reCAPTCHA project:
– It prevents website registration spam.
– It prevents bogus comments in blogs.
– It protects email addresses from scrapers.
– It can be used more accurate online polls.