What role do firewalls play in network security?

Firewalls play a crucial role in network security primarily by filtering all incoming and outgoing internet traffic. This filtering process helps to safeguard the network from unauthorized access, potential threats, and malicious activities. By establishing a barrier between a trusted internal network and untrusted external networks, firewalls control which data packets are allowed to enter or exit based on predetermined security rules.

This traffic filtering can be applied in multiple ways, such as allowing certain types of traffic (like web pages or email protocols) while blocking others (like unauthorized access attempts or suspicious activities). This capability is essential for protecting sensitive information and maintaining the integrity of network operations.

The other options, such as data encryption and creating user access restrictions, while important aspects of comprehensive security strategies, are not the primary functions of firewalls. Firewalls can aid in implementing access restrictions through defined rules but do not involve document shredding or direct data encryption processes. Thus, option B accurately represents the fundamental role of firewalls in ensuring network security.