Digital data processing systems of the type in which a server digital data device (“server”) is coupled to a client digital data device (“client”) over a network, e.g., the Internet, include web server software executing within an application layer on the server that responds to a request from the client by (i) validating a key received from the client with that request, (ii) generating a result code indicative of a success of that validation, (iii) initiating processing of the request, including invoking server resource software executing outside the application layer. The server resource software, which checks the result code upon invocation and before performing a protected operation required for processing the request, responds to a result code indicating that the result did not validate by exiting before executing the protected operation.