What is the primary function of a firewall?

The primary function of a firewall is to monitor and control network traffic. Firewalls act as barriers between trusted internal networks and untrusted external networks, such as the internet. Their main purpose is to allow or block data packets based on a set of security rules. By analyzing incoming and outgoing traffic, firewalls can prevent unauthorized access to or from a private network, thus protecting the system from potential threats such as hackers, malware, or other malicious entities.

In contrast, other functions mentioned in the options do not fall under the responsibilities of a firewall. Encrypting files relates to data security but focuses on protecting the contents of files rather than controlling network access. Backing up system data is essential for data recovery and resilience but does not pertain to network security. Updating system drivers involves ensuring that the hardware components of a computer operate correctly and efficiently but does not involve the monitoring or control of network traffic. Therefore, the answer emphasizing the firewall's role in network traffic management accurately reflects its core function.