PROTECTING AGAINST THE INTRODUCTION OF ALIEN CONTENT

In one implementation, a computer-implemented method can identify abnormal computer behavior. The method can receive, at a computer server subsystem and from a web server system, computer code to be served in response to a request from a computing client over the internet. The method can also modify the computer code to obscure operational design of the web server system that could be determined from the computer code, and supplement the computer code with instrumentation code that is programmed to execute on the computing client. The method may serve the modified and supplemented computer code to the computing client.