Dictionary · Networking Hardware
Firewall
Security devices · Beginner
A control that permits or denies traffic based on policy. It can be a dedicated appliance, a router feature, or host software, and it may inspect more than just addresses and ports.
It decides which conversations are allowed. A simple rule looks at address, port, and direction. A modern one may also track connection state and application behavior.
Picture it
Rules decide which conversations are allowed. Allowing encrypted web traffic out while denying unsolicited inbound connections is a policy. Address translation is a separate job.
Example: An edge policy allows encrypted web traffic out and denies unsolicited inbound connections to employee laptops.
Common misconception
- Address translation is not a firewall. A product can do both, but the security comes from the policy.