What is the primary function of a firewall?

The primary function of a firewall is to monitor and control incoming and outgoing network traffic. Firewalls serve as a security barrier between a trusted internal network and untrusted external networks such as the internet. By filtering traffic based on predetermined security rules, firewalls can allow or deny data packets, helping to prevent unauthorized access and protect sensitive information. This traffic management is essential for maintaining the security of servers and networks.

The other options describe different functions that are not related to the core purpose of a firewall. Managing file storage pertains to file system operations within a server, user authentication is a process to verify the identity of users accessing the system, and providing email services relates to data communication and management, which does not fall under the responsibilities of a firewall.