Computer systems and methods in various embodiments are configured for improving the security and efficiency of client computers interacting with server computers through an intermediary computer using one or more polymorphic protocols. In an embodiment, a computer system comprises a memory; a processor coupled to the memory; a processor logic coupled to the processor and the memory, and configured to: intercept, from a server computer, a first file and a second file, wherein the first file defines a first object with a first identifier and the second file comprises a reference to the first object by the first identifier; generate a second identifier; replace the first identifier with the second identifier in the first file; add one or more first instructions to the first file; remove the reference to the first identifier from the second file; add, to the second file, one or more second instructions, which when executed cause the one or more first instructions to be executed and produce the second identifier.