Firewall

Firewall: Controls network traffic based on defined rules and security policies. The control applies to network communicationNetwork CommunicationThe exchange of data between systems over network protocols and connections. or network accessNetwork AccessThe ability of a user, device, or workload to connect to and use network resources.. Effectiveness is achieved through restrictive rules, segmentation, continuous monitoringMonitoringThe continuous observation of systems, identities, networks, and controls for relevant changes., and coordinated response processesResponse ProcessA coordinated sequence of decisions and actions for handling security events and incidents..

How it works and where it fits

Firewall is a preventive, detective, or corrective security control. Its effect depends on where it sits in the architecture, which data and decisions it processes, and how it might be bypassed. A control reduces a defined risk but rarely removes it completely, so it should be combined with additional layers of protection.

Practical security relevance

Before deployment, the objective, ownership, coverage, and expected behavior should be defined. Secure defaults, controlled exceptions, logging, and periodic effectiveness tests matter more than installation alone. Operational metrics should expose both blocked or detected activity and gaps, false alerts, and effects on legitimate business processes.

Related concepts

• Web Application FirewallWeb Application FirewallFilters HTTP traffic to protect web applications against common attacks.: Filters HTTP traffic to protect web applications against common attacks.
• Next-Generation FirewallNext-Generation FirewallFirewall featuring application, identity, content, and threat controls.: Firewall featuring application, identity, content, and threat controls.
• Intrusion Detection SystemIntrusion Detection SystemDetects suspicious or anomalous activities on hosts or within networks.: Detects suspicious or anomalous activities on hosts or within networks.
• Network SegmentationNetwork SegmentationSeparates network segments to control access and limit lateral movement.: Separates network segments to control access and limit lateral movement.