What is the purpose of a firewall in network security?

A firewall serves a crucial role in network security by monitoring and controlling incoming and outgoing network traffic based on predetermined security rules. Its primary purpose is to create a barrier between a trusted, secure internal network and untrusted external networks, such as the internet.

By inspecting traffic and determining whether to allow or block specific data packets, a firewall helps prevent unauthorized access to or from a network. This can protect systems from malicious attacks, unauthorized access, and other security vulnerabilities. Firewalls utilize various methods, including filtering traffic based on IP addresses, protocols, and port numbers, as well as employing deeper packet inspection techniques to analyze the contents of the packets themselves.

The other options, while important aspects of network security and data management, do not define the primary function of a firewall. Encrypting data transmissions is related to securing the content of data against interception, managing user permissions pertains to access control within systems, and backing up network data focuses on data recovery practices. Each of these plays a vital part in an overall security strategy, but they do not encapsulate the core function of a firewall.