Different types of firewalls
1.Packet filtering firewalls This, the original type of firewall , operates inline at junction points where devices such as routers and switches do their work.However, this firewall doesn't route packets, but instead compares each packet received to a set of established criteria -- such as the allowed IP addresses, packet type, port number, etc. 2.Circuit-level gateways Using another relatively quick way to identify malicious content, these devices monitor the TCP handshakes across the network as they are established between the local and remote hosts to determine whether the session being initiated is legitimate -- whether the remote system is considered trusted. They don't inspect the packets themselves, however. 3.Stateful inspection firewalls State-aware devices, on the other hand, not only examine each packet, but also keep track of whether or not that packet is part of an established TCP session. This offers more security than either packet filtering or circ...