What does a firewall primarily do in a network?

A firewall's primary function in a network is to prevent unauthorized access to or from a private network. This is achieved through a set of predefined rules that govern the traffic allowed to enter or exit the network. By monitoring and controlling incoming and outgoing network traffic based on these rules, firewalls act as a barrier between trusted internal networks and untrusted external networks, such as the internet.

Firewalls can also log traffic, alert administrators to potential security incidents, and provide a level of security that mitigates risks from various external threats. Their key role is to establish and enforce security policies, making them essential components of network security infrastructures. While they may indirectly influence network performance, their primary focus is on security rather than speed or antivirus functions.