Which firewall policy is considered to be the most secure by default but usually requires more administrative work?

The choice of blocking all access by default, then allowing only necessary connections is recognized as the most secure firewall policy because it follows the principle of least privilege. This means that only the connections that are explicitly permitted are allowed through the firewall, minimizing the attack surface. By default, the firewall denies all traffic, which means that any potential vulnerabilities are inherently contained, and only specific, known safe connections are established.

This approach requires thorough planning and understanding of the network's needs, as any required service or connection must be specifically allowed through configuration. Consequently, it can lead to increased administrative workload, as each new application or service that needs to be accessed externally must be carefully defined and permitted in the firewall rules. This contrast with other policies emphasizes security over convenience, ensuring that the firewall operates with the highest level of protection against unauthorized access and potential cyber threats.