What is the primary function of a firewall?

The primary function of a firewall is to act as a barrier between trusted and untrusted networks. Firewalls are essential components in network security, as they monitor and control incoming and outgoing network traffic based on predetermined security rules. This involves inspecting packets of data to determine whether they should be allowed through or blocked based on their source, destination, and protocol used.

By effectively managing access between safe internal networks and potentially harmful external networks, firewalls help mitigate the risk of unauthorized access, attacks, and data breaches. They play a crucial role in establishing a security perimeter that safeguards sensitive information and ensures the integrity of internal systems.

Other options describe functions that, while important in the realm of IT, do not align with the core role of a firewall. Monitoring application performance pertains to evaluating the efficiency and responsiveness of software applications rather than managing network security. Encrypting network traffic refers to securing data during transmission to protect it from interception but does not describe the functions of a firewall itself. Lastly, backing up data regularly focuses on data preservation and recovery, which is unrelated to the firewall's security-oriented duties.