1. A method implemented by data processing apparatus, the method comprising: obtaining a software program that includes a set of program instructions for execution by the data processing apparatus; identifying different sections of program instructions from the set of program instructions of the software program, each of the different sections of program instructions corresponding to a different portion of the software program; selecting, for each of the different sections of program instructions and from among a plurality of sandbox methods that are available to the data processing apparatus, a respective sandbox method to apply during execution of the section of program instructions, wherein each of the plurality of sandbox methods comprises respective sandbox instructions for executing program instructions using fault isolation techniques that are different from fault isolation techniques of each other sandbox method of the plurality of sandbox methods, wherein the respective sandbox methods selected for at least some of the different sections of program instructions are different from each other; and causing execution of the software program using the respective sandbox methods selected for each of the different sections of program instructions.