AP® Cybersecurity glossary
Firewall
Software that allows or denies network traffic in or out of a network using a set of rules called an access control list (ACL); it runs on its own device or inside another one, such as a router.
Appears in the course and exam description (CED): 3.4.A.13.4.B.13.4.C.33.4.D.2
Why it matters in Unit 3
Unit 3 compares stateless, stateful and next-generation firewalls and expects a firewall at every point of ingress and egress.
Example
The rule “Deny inbound transmission control protocol (TCP) port 80 from 192.168.1.0/24” blocks web traffic from every address in that range.
Learn it properly, with a checkpoint Networks: hosts, packets and the devices that move them