Abstract: A computer system architecture, wherein a virtual machine and a virtual network bridge are controllable by a basic operating system, the virtual machine is linked to the virtual network bridge and set up for communication with further virtual machines within a virtual communication subnetwork, establishment of a connection from the virtual machine to an external physical network outside the physical computer system, which has a different configuration than the virtual communication subnetwork, is prevented, and the network ports of the physical computer system are set up such that relaying of a communication between the virtual machine and other virtual machines within the virtual communication subnetwork beyond the physical computer system by the external physical network (N, N1, N2) is permitted, but establishment of a connection from the external physical network from outside the physical computer system to the physical computer system independently of the virtual communication subnetwork is prevented.