• A firewall is a network security device that monitors and filters incoming and outgoing network traffic according to security regulations set by an organisation. A firewall, at its most basic level, is the barrier that separates a private internal network from the public Internet. The primary goal of a firewall is to allow non-threatening traffic in while keeping harmful traffic out.
• Filtering of packet A tiny amount of data is examined and delivered in accordance with the filter's requirements.
• Service of proxy-At the application layer, a network security system protects while filtering messages.
• Inquisitive inspection-Dynamic packet filtering keeps track of active connections to decide which network packets to let through the Firewall.
• Deep packet inspection is a feature of Next Generation Firewalls (NGFWs). Application-level inspection in a firewall.

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