What does a firewall primarily do?

A firewall primarily serves to enforce security policies and filter network traffic. It acts as a barrier between a trusted internal network and untrusted external networks, such as the internet. By examining incoming and outgoing traffic against predetermined security rules, a firewall can block or allow data packets based on various criteria. This filtering process helps prevent unauthorized access to or from a network, protecting sensitive information and maintaining the integrity of the system.

The other options do not accurately describe the primary function of a firewall. While some security solutions may protect against virus attacks, a firewall is not specifically designed for that purpose; its focus is on traffic regulation rather than malware detection. Monitoring employee activities relates more to network monitoring tools and is not a core function of firewalls. Lastly, data backup solutions are entirely separate entities that focus on the preservation and recovery of data, which does not fall under the capabilities of firewalls.