1. A computer-implemented method for determining a manner in which to re-code an electronic resource, comprising: receiving, by a computing system and as having been sent from a computing device remote from the computing system, a request for the electronic resource; identifying, by the computing system, a security token received from the computing device along with the request; identifying, based on a value of the security token that identifies a particular entity that submitted the request, a security policy assigned to the particular entity that submitted the request; selecting, based on the identified security policy assigned to the particular entity that submitted the request, a set of security countermeasures to apply to the electronic resource to be served in response to the request, the security countermeasures operating to interfere with an ability of malware to interact with the served electronic resource when the served electronic resource is on the computing device, wherein selecting the set of security countermeasures comprises selecting from among multiple different choices that include a first choice to apply no security countermeasures and a second choice to apply one or more particular security countermeasures; in response to selecting the second choice to apply the one or more particular security countermeasures, re-coding first portions of the electronic resource that are to be executed on the computing device using the one or more particular security countermeasures; and serving a re-coded electronic resource having the re-coded first portions and other portions to the computing device in satisfaction of the request.