Which of the following best describes a firewall's role in network security?

A firewall's role in network security is primarily about filtering network traffic based on predefined security rules. This involves examining incoming and outgoing traffic to determine whether to allow or block specific packets based on established criteria, which can include IP addresses, protocols, ports, and more. This function of a firewall helps to enforce a security policy by controlling access to networked systems and protecting sensitive information from unauthorized access.

In this context, while preventing malware infections, detecting cyber attacks, and managing user access are important security measures, they are not the primary function of a firewall. Preventing malware typically involves using antivirus software, detecting cyber attacks may involve intrusion detection systems, and managing user access is more related to access control policies and identity management solutions. Thus, the focus of the firewall is specifically on traffic filtering, making the distinction clear in the broader landscape of network security measures.