How to stop bots/scripts from using your forms?
A lot of unwanted mails you get as spams, previously it was only due to the mailto: format and occured mostly when you have put your mail id directly on the webpage. To avoid flooding of queries by sudden automatic filings and un-solicited subscription requests are the examples of bots/programs using your sites forms.
Now the solution for Webmasters ?
The Answer is CAPTCHA.
What is CAPTCHA ?
A “CAPTCHA” stands for “Completely Automated Public Turing test to tell Computers and Humans Apart”, trademarked by Carnegie Mellon University, and is a free service.
Mellon University Members Luis von Ahn, Manuel Blum, Nicholas J. Hopper along with John Langford of IBM are credited for coining the term CAPTCHA in 2000.
How CAPTCHA work?
The differentiation method between human and computers (basically programs)
use CAPTCHAs to protect against automated brute force attacks like these. Basically, a CAPTCHA foils a bot by posing a question that humans can answer easily, but a software program fails at. An example is reading distorted random text.