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Preventing Forum Spam-bots?
A concerned reader asks: "Recently it seems that forums have become the new target for spam bots advertising everything from porn to casinos. The forums that I admin are constantly harassed by these bots even though you must enter the visual confirmation code code (the picture with letters/numbers) as well as reply to an e-mail in order to register. This only started a few months ago so I'm suspecting that some new spam program was released that somehow gets around these anti-bot measures. How can I get rid of these annoying bots?"
Use a Captcha, which is a tool that displays a distorted image containing a word, or sequence of letters. The user must enter in the correct sequence in order to post.
Captcha's aren't perfect, some have readability problems for the people, and they completely exclude blind people unless you use an audio captcha as well.
Require completing captcha to create a new account, or post as a guest. Once users have an account and are logged in, you can drop the requirement to use the captcha on every post.