What are 'firewall rules' used for?

Firewall rules play a crucial role in network security by defining what type of traffic is permitted or denied through the firewall. They serve as guidelines that determine how incoming and outgoing packets are handled based on various criteria, such as IP addresses, protocols, and port numbers. This ensures that only authorized traffic is allowed, protecting the local network from potentially harmful or unwanted external connections.

In contrast to the chosen answer, while controlling data flow is an aspect of what firewalls do, it is not the primary definition of firewall rules. The focus is more on the explicit permission or denial provided by these rules. The options related to improving network speed and managing IP address conflicts do not pertain to the specific purpose of firewall rules, which are primarily about security and access control rather than performance optimization or conflict resolution.