Firewalls and Next-Generation Firewalls
The first line of defense — and what modern firewalls actually do.
Key takeaways
- Traditional firewalls filter by port/protocol; NGFWs add application awareness and deep packet inspection.
- Stateful firewalls track connection state, allowing return traffic for established sessions.
- Defense-in-depth means firewalls are one layer, not the only layer.
- Egress filtering is as important as ingress — it stops C2 callbacks and data exfiltration.
The firewall is often called the "front door" of network security — but a modern NGFW is really more like a trained security guard with a database of known threats, application signatures, and behavioral baselines.
Knowledge check
Why is egress filtering important even if your perimeter firewall blocks all inbound threats?