What is the significance of firewalls in network security?

Firewalls play a crucial role in network security by acting as a barrier between trusted internal networks and untrusted external networks. This function is essential because it controls the flow of incoming and outgoing traffic based on predetermined security rules, thereby protecting sensitive data and resources from unauthorized access and potential threats. By effectively filtering traffic, firewalls help to prevent malicious attacks, such as unauthorized intrusions, malware infiltration, and various forms of cyber threats.

While other elements mentioned in the choices contribute to network security in different ways, they do not encompass the primary purpose of firewalls. For instance, firewalls do not inherently increase network speed, nor do they store data backups or primarily limit user access to applications—they serve a specific function of controlling traffic and maintaining the integrity of networks. Hence, the significance of firewalls in creating secure network environments lies in their protective barrier function against external threats.