1. A computer-implemented method for security validation of a user input in a computer network application, the method comprising the steps of: providing a subset of security rules of a server-side protection means to a pre-validation component deployed at a client side, so as to enable security validation of a user input on the client side by the pre-validation component based on the provided security rule subset; validating the user input based on at least one of the security rules of the server-side protection means; determining, in response to detecting a user input violation and that a violated security rule has not been provided to the pre-validation component, the user as one of a first class of users; determining, in response to detecting a the user input violation and that the violated security rule has been provided to the pre-validation component, the user as one of a second class of users; and performing different security protection actions to the determined first class of users and the determined second class of users, wherein the step of performing different security protection actions to the determined first class of users and the determined second class of users comprises: performing, to the second class of users, a security protection action as compulsorily blocking all subsequent requests, and performing, to the first class of users, a security protection action which maintains access to the computer network application.