Each virtualized environment on a computer has its own set of firewall rules. The virtualized environments share a single instance of the operating system image, a filter engine and a single network stack. A virtualized environment may be a compartment or a server silo. A virtualized environment is a network isolation mechanism and may be used to prevent use of a computer to traverse network boundaries by creating a separate virtualized environment for each network, enabling a separate set of rules to be applied to each virtualized environment and the network interfaces within it. Virtualized environments may also be used to assign different trust levels to the same physical network. Firewall rules are applied by virtualized environment identifier (ID), enabling separate filters to be applied to each virtualized environment on a computer. A virtualized environment may include or be associated with one or more network interfaces.