guard

In information security, a guard is a device or system for allowing computers on otherwise separate networks to communicate, subject to configured constraints. In many respects a guard is like a firewall and guards may have similar functionality to a gateway. Whereas a firewall is designed to limit traffic to certain services, a guard aims to control the information exchange that the network communication is supporting at the business level. Further, unlike a firewall a guard provides assurance that it is effective in providing this control even under attack and failure conditions. A guard will typically sit between a protected network and an external network, and ensure the protected network is safe from threats posed by the external network and from leaks of sensitive information to the external network. A guard is usually dual-homed, though guards can connect more than two networks, and acts as a full application layer proxy, engaging in separate communications on each interface. A guard will pass only the business information carried by the protocols from one network to another, and then only if the information passes configured checks which provide the required protection.