A virtualization framework provides security between multiple virtual machines with respect to network communications between the virtual machines and between the virtual machines and a physical network coupled to the underlying physical computer platform. The virtualization framework includes a network interface controller driver that provides an interface to the platform network interface controller and supports execution of a plurality of virtual machines. Each virtual machine includes a virtual network interface controller that provides a network communications path between the virtual machines and to the network interface controller driver. Each virtual network interface controller further contains a programmable network packet filter that controls the selective transfer of network packets with respect to a corresponding virtual machine.