CaptchaMvc.Mvc4 (nuget): CaptchaMvc will implement your web MVC applications easier and more reliable protection. Features: You can easily change or extend the current implementation of the captcha.  By default there are two types of captcha, plain and mathematical. Supports MVC 3, MVC 4, MVC 5. Supports for storing captcha in the session or cookie. Supports the "intelligent" captcha.
Keywords: captcha|asp.net|mvc|mvc4|C#