LoopbackAuthorisationFilter

gistfile1.cs

public class LoopbackAuthorisationFilter : System.Web.Http.Filters.AuthorizationFilterAttribute
    {
        public override void OnAuthorization(HttpActionContext actionContext)
        {
            // Play nicely with the base class :)
            base.OnAuthorization(actionContext);

            // If the request does not originate from this machine
            if (!System.Web.HttpContext.Current.Request.IsLocal)
            {
                // Create an Unauthorised Access response
                actionContext.Response = actionContext.Request.CreateResponse(HttpStatusCode.Unauthorized, "Unauthorised Access");
            }
        }
    }