ips

Today, most networks are protected by firewalls. Even home users get the idea. There are numerous types of firewall, but they all work in the same way: allow in the authorised traffic, filter the rest. The majority of pure bred firewalls do not apply any further filtering on the traffic beyond IP and service port values. In the beginning it was as simple as blocking IP addresses and filtering ports. The first firewalls didn't even understand ports.