1. Packet-Filtering Firewalls: These are the most basic type of firewalls, which use a set of rules to decide which packets to allow or deny based on the source and destination IP addresses, port numbers, and protocols. Example: Cisco ASA Firewall.
2. Stateful Inspection Firewalls: These firewalls inspect each packet and keep track of the state of the connection. This allows them to make decisions about whether to allow or deny the packet based on the context of the connection. Example: Check Point Firewall.
3. Application-Level Firewalls: These firewalls inspect traffic at the application layer, which allows them to make decisions about whether to allow or deny traffic based on the application that is being used. Example: Web Application Firewall (WAF).
4. Next-Generation Firewalls: These firewalls combine the features of packet-filtering firewalls, stateful inspection firewalls, and application-level firewalls into a single solution. Example: Palo Alto Networks Firewall.