Custom Authorization in ASP.NET MVC through a custom Authorization attribute.

CustomAuthorize.cs

public class CustomAuthorizeAttribute : System.Web.Mvc.AuthorizeAttribute
{
    protected override void HandleUnauthorizedRequest(System.Web.Mvc.AuthorizationContext filterContext)
    {
        // Clear Cookies
        // Put your code here

        base.HandleUnauthorizedRequest(filterContext);
    }
}