CyberGuard dictionary / Network Security
Firewall
A device or program that controls network traffic according to security rules.
In simple terms
A firewall acts like a checkpoint for traffic entering or leaving a network or device.
Technical explanation
Packet, stateful, and application-aware firewalls make different decisions using addresses, ports, connection state, or application context.
Rules should describe permitted flows between specific sources, destinations, ports, and applications, with logging and regular review. A firewall cannot correct an application flaw in traffic it is configured to allow.
Examples in practice
A company blocks unexpected inbound connections to a database server.
The database accepts connections only from the application tier. When a staff laptop tries to connect directly, the firewall rejects and logs the attempt for review.
Why it matters
A firewall can narrow exposure but cannot identify every harmful action in allowed traffic.
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Sources and further reading
Published 2026-10-15 · Last updated 2026-10-15 · CyberGuard editorial content. Source links provide context; they do not imply endorsement.