Summary
A firewall enforces access control between network segments by inspecting packets and applying rules that permit or deny traffic based on source, destination, port, and protocol.
What is a Firewall?
Firewalls are the foundational perimeter security control in any network. Packet-filtering firewalls operate at the network layer, evaluating each packet against a set of rules without tracking connection state. Stateful firewalls track active connections and allow return traffic automatically, reducing rule complexity.
Next-generation firewalls (NGFW) add deep packet inspection, application awareness, and integration with threat intelligence feeds. They can identify and block specific applications or protocols regardless of the port used.
In cloud environments, traditional hardware firewalls are often replaced or supplemented by virtual firewalls, security groups, and network ACLs. These software-defined controls are provisioned via API and can scale dynamically with the workload.
Why is Firewall relevant?
- Perimeter security: First line of defence against unauthorised access to network resources
- Segmentation: Isolates network zones to limit lateral movement in the event of a breach
- Compliance: Many regulatory frameworks require documented firewall rules and regular audits