17. A system comprising: one or more computers and one or more storage devices storing instructions that are operable, when executed by the one or more computers, to cause the one or more computers to perform operations comprising: identifying a plurality of computing devices, each computing device of the plurality of computing devices having a software component comprising a first translator component for translating a programs in a portable format to a machine-specific instruction set, and a first sandbox component for executing programs translated to the machine-specific instruction set on the computing device using software-based fault isolation; identifying one or more second computing devices, from among of the plurality of computing devices, that have a given hardware configuration; and transmitting a second translator component and a second sandbox component to each of the second computing devices wherein each of the second computing devices is configured to: (i) receive the second translator component and the second sandbox component, and (ii) configure the software component of the second computing device to use the second translator component instead of using the first translator component to translate programs in the portable format to a machine-specific instruction set of the second computing device and to use the second sandbox component instead of using the first sandbox component to execute programs translated to the machine-specific instruction set of the second computing device.
17. A system comprising: one or more computers and one or more storage devices storing instructions that are operable, when executed by the one or more computers, to cause the one or more computers to perform operations comprising: identifying a plurality of computing devices, each computing device of the plurality of computing devices having a software component comprising a first translator component for translating a programs in a portable format to a machine-specific instruction set, and a first sandbox component for executing programs translated to the machine-specific instruction set on the computing device using software-based fault isolation; identifying one or more second computing devices, from among of the plurality of computing devices, that have a given hardware configuration; and transmitting a second translator component and a second sandbox component to each of the second computing devices wherein each of the second computing devices is configured to: (i) receive the second translator component and the second sandbox component, and (ii) configure the software component of the second computing device to use the second translator component instead of using the first translator component to translate programs in the portable format to a machine-specific instruction set of the second computing device and to use the second sandbox component instead of using the first sandbox component to execute programs translated to the machine-specific instruction set of the second computing device. 24. The system of claim 17 , wherein identifying the one or more second computing devices that have the given hardware configuration comprises selecting the second computing devices based on a characteristic of one or more microprocessors of the second computing devices.