Abstract: A computer-implemented method for identifying abnormal computer behavior includes receiving, at a computer server subsystem, data that characterizes subsets of particular document object models for web pages rendered by particular client computers; identifying clusters from the data that characterize the subsets of the particular document object models; and using the clusters to identify alien content on the particular client computers, wherein the alien content comprises content in the document object models that is not the result of content that is the basis of the document object model served.

Abstract: A computer-implemented method for coordinating content transformation includes receiving, 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; modifying the computer code to obscure operation of the web server system that could be determined from the computer code; generating transformation information that is needed in order to reverse the modifications of the computer code to obscure the operation of the web server system; and serving to the computing client the modified code and the reverse transformation information.