1. Packet Filtering Firewalls: These are the most basic type of firewalls, which inspect and filter incoming and outgoing network traffic based on source and destination IP addresses, port numbers, and protocols. Example: Cisco PIX Firewall.
2. Stateful Inspection Firewalls: These firewalls inspect both incoming and outgoing traffic and keep track of the state of each connection. They are more advanced than packet filtering firewalls and can detect malicious traffic more effectively. Example: Cisco ASA Firewall.
3. Network Address Translation (NAT) Firewalls: NAT firewalls provide an additional layer of security by hiding the internal network IP addresses from external networks. Example: Cisco ASA Firewall.
4. Application-Level Firewalls: These firewalls are used to filter traffic based on the application layer of the OSI model. They are more advanced than packet filtering firewalls and can detect malicious traffic more effectively. Example: Check Point Firewall.
5. Proxy Firewalls: Proxy firewalls act as an intermediary between the internal network and the external network. They inspect all incoming and outgoing traffic and can filter traffic based on application layer protocols. Example: Microsoft ISA Server.