In this video, you will learn to; describe the difference between a stateful and a stateless firewall, describe the trade offs when moving from the stateless to stateful firewall. Okay. So next up, we're going to talk a little bit about firewalls. Firewalls as you already probably know can fills the truck would be between networks. Depending on the type of firewalls, they handle packets differently. Firewalls can be multi-homing as well, meaning they have multiple and mixed explorer interface connectors connected to different networks that's basically to put in other words, we have one new connected to Internet, and then we have one big connected to our local network. They are also different types of firewalls, but we'll go over a few of them stateless and stateful which are the most common ones in a loyalty to the latter one the more secure one. So stateless firewalls as the word says, they have no concept of the state. It can also be called packet filters. They make their decisions based on layer three and layer four information meaning IP and port. They lacked the sense of the state, and of course, they're less secure. As you can see from the image shown here on your left, on the top you see ICMP echo request and the corresponding ICMP reply via accepted bug firewall. But on the bottom, the attackers just sending equal replies that it's not preceded by an echo request, and the packet filter on the stainless firewall actually allows them packets through. On a stateful firewalls that we will see next, that echo reply if it's not followed by an echo request would be denied firewall. Stateful firewalls, they have a state tables basically allowed the firewall to compare current packets with previous packets. This actually makes the firewall a little bit slower, but far more secure than their stateless firewall. Sometimes they're also called application firewalls, and they can make decisions based on layer 7 information meaning they could also filter information based on the type of website that somebody is listening. As you can see from the image on your left, ICMP echo requests and then the corresponding echo required by being accepted by when an effect that tries to send an ICMP echo reply. The stateful firewall will go to the state table, detect that at echo required has no corresponding previous echo requests and block that traffic with the night. There's one more type of firewall that we'll discuss in they called proxy firewalls. They basically act as an intermediary server. As you can see from the image below, iIt's between two nodes of course computer and the server. But actually terminates the connection once the computer initiative and the connection with the bug. As you can see also it has as two and 3-way handshakes between two devices meaning computer would initiate a connection with the server, but the firewall will actually make that connection back to computer one, and then the proxy firewall will initiate another connection with the bug itself. So it should be between two devices like a man in the middle, and this will allow the proxy firewalls to filter a bunch of tracking can actually analyze them even better.