An inter-network connection device that restricts data communication traffic between two connected networks. A firewall may be either an application installed on a general-purpose computer or a dedicated platform (appliance), which forwards or rejects/drops packets on a network. Typically firewalls are used to define zone borders. Firewalls generally have rules restricting which ports are open.

See NIST SP 800-82 Rev. 2 under Firewall from ISA-62443-1-1 for more information.

A gateway that limits access between networks in accordance with local security policy.

See the following for more information:
CNSSI 4009-2015
NIST SP 800-12 Rev. 1 under Firewall
NISTIR 7621 Rev. 1 under Firewall

A part of a computer system or network that is designed to block unauthorized access while permitting outward communication.

See the following for more information:
NIST SP 1800-27B under Firewall from NIST SP 800-152
NIST SP 1800-27C under Firewall from NIST SP 800-152
NIST SP 800-152
under Firewall

A device or program that controls the flow of network traffic between networks or hosts that employ differing security postures.

See NIST SP 800-41 Rev. 1 under Firewall for more information.

A firewall is a device that has a network protection application installed to safeguard the network from intentional or unintentional intrusion. A firewall sits at the junction point or gateway between the two networks, usually a private network and a public network such as the Internet. The term “firewall” is derived from the process in which, by segmenting a network into different physical subnetworks, the firewalls limit damage that could spread from one subnet to another, acting in the same manner as fire doors or firewalls in automobiles.

See NIST SP 800-35 for more information.

A system designed to prevent unauthorized accesses to or from a private network. Often used to prevent Internet users from accessing private networks connected to the Internet.

See NISTIR 7316 under Firewall for more information.

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