A data transfer system includes a set of switch and/or router devices (104B, 104E, 104F), each said device in the set being a layer 1, 2 and/or 3 device of OSI seven-layer model and being configured, in use, to transfer data, directly or indirectly, between a plurality of computing devices (102A, 102B). Each said switch or router device in the set is configured to provide a virtual partition (VP), wherein only data designated as virtual partition data is transferrable to another said device in the set via the virtual partition.