Packet Filtering Firewall:
Packet filtering firewalls are the most basic type of firewall.
They inspect packets and filter them based on predetermined rules.
These rules determine which packets are allowed to pass through the firewall and which packets are blocked.
Packet filtering firewalls operate at the network layer (Layer 3) of the OSI model and can only inspect packets based on IP address, port number, and protocol.
They cannot inspect the contents of the packets. Packet filtering firewalls are simple to set up and are usually less expensive than other types of firewalls.
Stateful Inspection Firewall:
Stateful inspection firewalls, also known as dynamic packet filtering firewalls, operate at the transport layer (Layer 4) of the OSI model.
They not only inspect packets based on IP address, port number, and protocol but also check the state of the connection.
Stateful inspection firewalls keep track of the connections between hosts and only allow packets that are part of an established connection.
This helps prevent attacks that use spoofed IP addresses to bypass the firewall.
Application Firewall:
Application firewalls, also known as proxy firewalls, operate at the application layer (Layer 7) of the OSI model.
They can inspect the contents of packets and filter traffic based on the application-level data.
Application firewalls are used to secure web applications, email servers, and other network services.
They can also provide additional security features such as content filtering, intrusion prevention, and antivirus protection.
Next-Generation Firewall:
Next-generation firewalls (NGFW) are a more advanced type of firewall that combines the features of traditional firewalls, intrusion detection and prevention systems (IDS/IPS), and application firewalls.
NGFWs are designed to provide more granular control over network traffic and are capable of deep packet inspection.
They can also integrate with other security technologies, such as VPNs and endpoint protection, to provide a more comprehensive security solution.