Using Captcha for spam prevention
For all blog readers who do not know what captcha is – it is an acronym for "Completely Automated Public Turing Test to tell Computers and Humans Apart". I'm sure you know these challenge-response tests on websites where you have to retype letters from a picture to prove that you are a real human being. Of course we may become annoyed because captcha needs time and it isn't always that easy to decipher the correct letters. But typically we will do the captcha test without getting too irritated, because we know it is helpful in spam prevention.
Unfortunately though, some clever people found a way to outfox captcha. Spammers may hire low-paid individuals from India or China for instance and let them make spam entries in blogs, guestbooks, and other online services. For a webmaster this is highly aggravating, especially when he has integrated captcha to serve exactly this purpose, yet still becomes flooded with spam.
What does this teach us? That the bad spammers always find a way! Even though this fact stands strong, we should not forget how much spam Captcha averts every single day, and be grateful for this help
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