It’s about time. We are now on Instagram!
A means of separating a computer network from outside networks for security purposes. A server outside an organization's own network may be used to funnel all incoming and outgoing traffic to assist in keeping out viruses, as well as to prevent unauthorized outsiders from gaining access to a network.
[fr a firewall built to contain a fire in a building, a meaning found by 1851, and a barricade between an engine and a passenger compartment, found by 1947]