A firewall is a network security system that monitors, filters, and controls incoming and outgoing network traffic based on a set of predefined security rules. Its primary purpose is to establish a barrier between a trusted internal network and untrusted external networks, such as the internet, to prevent unauthorized access and protect against malicious threats

. Firewalls work by inspecting data packets traveling through the network and deciding whether to allow or block them according to security policies. They act as gatekeepers, scrutinizing each packet to ensure only safe and legitimate traffic passes through. Firewalls can be implemented as hardware devices, software applications, or cloud-based services

. Modern firewalls, often called next-generation firewalls (NGFWs), include advanced features such as deep packet inspection, application visibility and control, intrusion detection and prevention, malware defense, and URL filtering to enhance network security

. In summary, a firewall is a critical security tool that protects networks by regulating traffic flow and blocking potentially harmful data, thereby safeguarding sensitive information and network resources from cyber threats