MSCABImage (captcha code) is the best cure from nasty posting bots (robots). These bots create hundreds email accounts on your web-based mail servers and spam from them, fill your forums with thousands of commercial postings and screw your online polls.
How it works. ABImage Component generates random number and make a hard-to-recognize picture from it. Your Web Application asks visitor to read the number and type it in a textbox. Human can easily recognize the number, but there is no way how a bot can do that. As soon as the form will be posted back, application compare the random number with the number posted by visitor and authorize a human or reject a bot.
The number can be generated by internal random number generator or can be set by the application.
Image can be extra protected from recognition with adding random noise.