A device or application for protecting a network or host against hostile network traffic.
A piece of software (or a combination of hardware and software) that isolates an intranet from the Internet, allowing only trusted traffic to travel between them.
A combination of hardware and software that separates a Network into two or more parts for security purposes.
A security system intended to protect an organization’s network against external threats, such as hackers, coming from another network, such as the Internet. Usually a combination of hardware and software, a firewall prevents computers in the organization’s network from communicating directly with computers external to the network and vice versa. Instead, all communication is routed through a proxy server outside of the organization’s network, and the proxy server decides whether it is safe to let a particular message or file pass through to the organization’s network. See also proxy server.