Firewall
A firewall is a security measure, which can be implemented as either a hardware or software solution, designed to filter network traffic. Operating on an implicit deny principle, a firewall blocks all incoming and outgoing traffic by default. However, rules, filters, or Access Control Lists (ACLs) can be configured to specify which types of traffic are permitted to traverse the firewall. Advanced firewalls have the capability to make allow or deny decisions based on various criteria such as user authentication, protocols, header values, and even the contents of the data payload, enabling more granular control over network traffic and enhancing overall security posture.