Which of the following best describes a firewall?

A firewall is primarily a security system designed to prevent unauthorized access to or from a private network. This is achieved through a set of predetermined security rules that either allow or block traffic based on various criteria such as IP addresses, port numbers, and protocols. Firewalls can be implemented in both hardware and software formats, providing a first line of defense against potential cyber threats, unauthorized users, and malicious entities trying to access sensitive information or services.

The function of a firewall is crucial in maintaining the integrity, confidentiality, and availability of data within a network. By monitoring and controlling incoming and outgoing network traffic, firewalls help safeguard the system against various attacks, including malware and intrusion attempts.