What is a common purpose of using a firewall in network security?

A firewall serves a critical function in network security by blocking unauthorized traffic. Its primary role is to act as a barrier between a trusted internal network and untrusted external networks, such as the internet. By filtering incoming and outgoing traffic based on predetermined security rules, a firewall helps prevent unauthorized access to sensitive information and protects against various cyber threats, such as hacking attempts and malware infiltration.

In contrast, providing high-speed internet access focuses on connectivity and performance rather than security. While monitoring user activity can be valuable for identifying potential security concerns or compliance violations, it is not the main purpose of a firewall. Similarly, encrypting sensitive data is an essential part of securing information, but this task falls under different security measures like encryption protocols rather than the primary function of a firewall.