Firewall What is a Firewall? A firewall is a cybersecurity tool that monitors and controls incoming and outgoing network traffic based on predefined security rules, protecting systems from unauthorised access and threats. Explanation Firewalls can be hardware-based, software-based, or a combination of both. They act as a barrier between internal networks and external sources, filtering traffic to prevent malicious activity. Practical Example of a Firewall A business installs a firewall to block unauthorised attempts to access its internal network while allowing safe communication with external partners.