What is the primary function of a firewall?

The primary function of a firewall is to monitor and control incoming and outgoing network traffic based on predetermined security rules. Firewalls serve as a barrier between a trusted internal network and untrusted external networks, such as the internet. By examining packets of data transmitted over the network, the firewall can allow or block traffic depending on whether it meets the organization's security policies. This enforcement helps prevent unauthorized access, attacks, and data breaches, ensuring that only legitimate traffic is allowed through.

In contrast, encrypting sensitive data is a different function, primarily aimed at protecting confidentiality, while acting as a proxy server deals with directing requests and responses between clients and servers, rather than simply controlling traffic flow. Performing data backups is another distinct activity that focuses on safeguarding data by creating copies for recovery purposes and is not a function associated with firewalls.