What function does a firewall perform in a computer network?

A firewall functions as a security system for a computer network, primarily through its ability to control data that travels in and out of the network. The correct answer emphasizes its role in denying specific types of incoming traffic, which is crucial for protecting the network from unauthorized access and potential threats such as malware or hacking attempts.

Firewalls operate based on predefined rules that determine which traffic is allowed and which is blocked. This selective filtering is integral to maintaining network integrity and security. By denying traffic that does not meet certain criteria, firewalls help to safeguard sensitive data and resources, ensuring that only trusted and safe communication is permitted.

While connecting different networks, managing bandwidth, and monitoring network traffic are important functions in networking, these tasks do not specifically capture the primary security function of a firewall, which revolves around controlling the flow of incoming and outgoing traffic based on specified security rules.