What can a firewall protect against?

A firewall can protect against unauthorized access to a network by monitoring and controlling incoming and outgoing traffic based on predetermined security rules. It can help defend against various threats, including malware, hacking attempts, and denial-of-service attacks. Additionally, firewalls can safeguard sensitive data by blocking potentially harmful connections and filtering out malicious traffic. However, it's important to note that while firewalls are effective, they should be part of a comprehensive security strategy that includes other measures.