Mitigating scripted attacks using dynamic polymorphism

A data processing method of improving resistance of a client computer to attacks comprising:

• at an intermediary computer:
• obtaining a particular electronic document from a server computer;
• inserting a set of script code into source code of the electronic document to result in producing a modified electronic document;
• providing the modified electronic document to a client computer;
• wherein the script code is configured to:
• improve resistance of the client computer to attacks by running upon loading in the client computer and to cause transforming, when running in the client computer, one or more values of one or more elements of the source code of the electronic document into obfuscated values of the one or more elements,
• repeatedly periodically execute in the client computer after loading in the client computer, and
• cause the transforming in a different manner at each time that the script code repeatedly executes in the client computer.

A data processing method of improving resistance of a client computer to attacks comprising:

• using a security computer that is logically interposed between a server computer that generates HTML documents and a client computer, obtaining a HTML electronic document from the server computer;
• inserting a set of JAVASCRIPT script code into HTML source code of the HTML document to result in producing a modified HTML document;
• providing the modified HTML document to the client computer;
• wherein the JAVASCRIPT code is configured to:
• improve resistance of the client computer to attacks by running upon loading in the client computer and to cause transforming, when running in the client computer, one or more values of one or more elements of the HTML source code of the HTML document into obfuscated values of the one or more elements,
• repeatedly periodically execute in the client computer at time intervals specified using a time interval value in the JAVASCRIPT code after loading in the client computer, and
• periodically updating the time interval value in the JAVASCRIPT code to a different time interval value.