A network mediator corresponding to a computing device uses packet filters
to restrict network communications. The network mediator includes a set
of one or more filters, each filter having parameters that are compared
to corresponding parameters of a data packet to be passed through the
network mediator. The network mediator determines whether to allow the
data packet through based on whether the data packet parameters match any
filter parameters. The set of filters can be modified by a remote device,
but cannot be modified by the computing device whose communications are
being restricted. When a data packet is sent from the computing device,
the data packet will include the virtual address which is changed to the
network address by the network mediator prior to forwarding the packet on
the network, and vice versa. By virtualizing the addresses, the computing
device is restricted in accessing other devices over the network.