Recaptcha - Killing two birds with one stone!

Spammers try to get free email accounts so they can send more spam or add spam comments to some blogs to help promote their website. That's probably the main use of Captchas these days to identify real humans and prevent automated signups. Though that doesn't help when you get people filling in captchas for 75c per thousand! Captcha is short for "Completely Automated Public Turing test to tell Computers and Humans Apart" and the term is trademarked by Carnegie Mellon University.

The second target bird is that of scanning old texts which are difficult to scan in accurately. The recaptcha dialog shows two words- making it harder to process by computer. The first word is an existing correctly processed word- so the chances are that if the user enters that correctly then the second one can be assumed to be correctly identified- especially if a number of people return the same word for it. If you have an ASP.NET website, you can get a free library to put recaptcha on your site. Recaptcha is written in C# and I've added a link to the C# Code Library.

• Link to C# Code Library