What is a firewall?

A firewall is a network security device that controls and monitors incoming and outgoing network traffic based on predetermined security rules. Its primary function is to establish a barrier between a trusted internal network and untrusted external networks, such as the internet. By filtering traffic and allowing or blocking data packets according to the established rules, firewalls help prevent unauthorized access and protect sensitive information.

Firewalls can be configured to protect a network against various threats, such as malware, hacking attempts, and denial-of-service attacks. They can operate at different levels, including hardware (dedicated devices) and software (applications running on servers or computers).

Understanding the role of a firewall is crucial in implementing effective network security measures, making it a foundational concept in computer security practices.