A client recently complained about getting alot of "spam" through a contact form posted on their website. Basically, automated "bots" are submitting bogus information (usually of a promotional nature) through the form. The same problem often plagues blogs allowing readers to post comments via forms.
A simple solution is to work with a provider who can offer "CAPTCHA" technology with their forms creation tool. For example, Typepad offers this technology with their "Comments" feature.
What's CAPTCHA? As explained by Wikipedia:
A CAPTCHA is a type of challenge-response test used in computing to ensure that [a] response [was provided by a human and not] a computer. The process usually involves one computer . . . asking a user to complete a [CAPTCHA] test which the computer is able to generate and grade. Because other computers are unable to solve the CAPTCHA, any user entering a correct solution is presumed to be human. A common type of CAPTCHA requires that the user type the letters or digits of a distorted image that appears on the screen.
This definition is actually inherent in the term CAPTCHA, which stands for "Completely Automated Public Turing test to tell Computers and Humans Apart."
In any event, by asking users to plug in a number or phrase displayed as an image at the bottom of a form, you can generally block automated bots that can't read the image from submitting bogus data (note: as detailed in the Wikipedia entry referenced above, not all CAPTCHA's are fool-proof with various methods having been devised to circumvent some of them depending on the technology used. Well, that's life on the Internet - the "good guys" devise safeguards, and the "bad guys" try to get around them).
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