What role do firewalls play in cybersecurity?

Firewalls play a critical role in cybersecurity by monitoring and controlling incoming and outgoing network traffic based on predetermined security rules. This functionality serves as a barrier between a trusted internal network and untrusted external networks, such as the internet. By analyzing the data packets as they attempt to pass through, firewalls can block or allow traffic based on its source, destination, and other attributes. This helps prevent unauthorized access to sensitive data, mitigates potential threats such as hacking attempts and malware, and ensures that only legitimate traffic is allowed through.

The significance of this role is underscored by the limitations of the other options. For instance, while firewalls do provide a layer of security that can influence overall network performance, their primary function is not to increase network speed. Allowing unrestricted internet access would severely undermine the security that a firewall is meant to provide. Lastly, enhancing data quality is not a function of firewalls; rather, it is more related to data management and governance practices. Thus, the central function of firewalls lies in their ability to monitor and control network traffic, making option C the correct choice.