A filtering router which checks packets of data which are destined for a closed network such as an intranet. If the data is directly allowed into the network then it passes through. If it is not allowed to pass through, two conditions may hold. The first is that the packet may be destined for a proxy server; in this case the packet is sent to that computer and processed there. The second is that the packet has been sent by a user who is not allowed access to the network; in this case it is rejected. Firewall routers are also known as packet filtering gateways or screening routers. See also bastion host.