What does a firewall primarily protect against?

A firewall primarily serves as a barrier that monitors and controls incoming and outgoing network traffic based on predetermined security rules. Its main function is to protect against unauthorized access to or from a private network. This includes preventing malware from entering the network, as well as blocking malicious activities that could exploit vulnerabilities in devices or applications.

By filtering traffic, a firewall can effectively stop potentially harmful data packets from reaching a device or server, thereby safeguarding sensitive information and maintaining the integrity of the network. It creates a controlled environment that only permits legitimate and safe communications, significantly reducing the risk of cyber attacks and data breaches.

The other options, while relevant to network management and security in different contexts, do not capture the primary protective function of a firewall. Software updates ensure that systems are current and less vulnerable to exploits, hardware failures relate to physical device issues, and network congestion pertains to traffic management rather than security threats.