Which of the following best describes the purpose of a firewall?

Firewalls serve a crucial role in network security by acting as a barrier between a trusted internal network and untrusted external networks, such as the internet. Their primary purpose is to monitor and control incoming and outgoing traffic based on predetermined security rules. By doing so, they help to prevent unauthorized access to or from a private network, safeguarding sensitive data and resources from potential cyber threats.

Option B accurately captures this essential function of firewalls. They analyze data packets and decide whether to allow or block them based on established security protocols, thereby reducing the risk of attacks, unauthorized users, and various forms of malicious activity.

In contrast, the other options describe functions that are not related to the primary purpose of a firewall. Backup solutions relate to data recovery rather than network security; software updates are important for maintaining system integrity and functionality, but they do not describe the role of a firewall; enhancing network speed focuses on performance rather than security measures. Thus, the focus on preventing unauthorized access highlights the critical role a firewall plays in maintaining a secure network environment.