A software system for installation on computing apparatus (and a method of installing such a software system on computing apparatus), wherein the software system is provided in the form of a software package including a plurality of software components, one or more of the software components being provided as a plurality of different implementations, the apparatus including an installation engine for installing the software system only a selected one implementation of the or each of the software components having multiple implementations, and a random selector module for selecting one of the plurality of implementations of a software component for installation. Thus, software package would still be distributed to its consumers as a single version but each installation of the package on a user's computing apparatus is potentially different, which reduce the risk of faults in and attacks against software components having one or more "bugs" therein because not all consumers will have the same implementation of any one software component.