What is the main function of a firewall in network security?

The primary function of a firewall in network security is to prevent unauthorized access to or from a network. Firewalls serve as a barrier that monitors and controls incoming and outgoing network traffic based on predetermined security rules. By doing so, they help protect the internal network from various threats, including unauthorized access attempts, malicious attacks, and data breaches.

Firewalls can be implemented in hardware, software, or both, and they play a crucial role in establishing a secure perimeter. They can block potentially harmful traffic while allowing safe communication, thereby enhancing the overall security posture of the organization.

In contrast, the other options presented do not accurately capture the main function of a firewall. Monitoring employee productivity, for example, is typically managed through other software solutions designed for employee management, and segregating network traffic, while related to security, is more of a function of network architecture practices than a direct firewall role. Lastly, improving internet connection speeds is not a purpose of firewalls; their focus is on security rather than performance optimization.