Hi folks Ed Amarosa here. Now listen, as you progress in your understanding of cyber security you're going to realize that as you do real time situationally aware cyber protection, cyber defense. One of the things a lot of security engineers know, and do, and almost have fun with is understanding and knowing and memorizing the well known ports of different types of services. Like we say port 80, yeah, it's HTTP, right? Everybody sort to knows that. And there's older ones that they know and it's just sort of fun, you may want to go dig in and take a look. But, the reason that's important here is that, we'll show you here on the screen. These are the rules that are in place for an HTTP Outbound browsing session from an enterprise that has a firewall protecting its users. In order to make changes to this rule, for many types of services, it turns out to be pretty easy. I think I told you about in some subsequent discussions, we talked about Telnet, that's port 23. If I want to take this canonical setup for HTTP and just have the rules in place for Telnet, then what do I do? Bing, I just changed 80 to 23 and the rest stays the same, that kind of rocks, doesn't it? Like it makes it a little easier to think through how you might set these things up. And then if I decide, hey I want to do SMTP, well that's 25. Bing, I changed it to port 25. And I have the same canonical set up. There are some short cuts here, right? It's not always this tedious processes of having to go through it. Look here's my heart felt advice to you, if you enjoy this sort of thing, if you enjoy packet filtering and setting up rules and so on. You have to learn TCP/IP, you have to learn the protocol, you have to learn the suite, you have to learn the vagarities of each of these different types of services like SMTP, Simple Mail Transfer Protocol, or Telnet or HTTP. Even if they don't necessarily show up in your network. You have to know these things because hackers will try to use them. Hackers don't care that people don't use Telnet anymore. They're going to see if you've got it sort of sloppily set up on your network. You've gotta keep track of these things, a lot of times my friends will say, why do you use these old protocols in your examples? Why don't you use newer ones? Gaming stuff and I'll say well, because hackers don't care if it's old I use whatever they think they can through. With in fact in many cases, the older protocols are best because you may have an old legacy rules that's there that you forgot to pull out and will take full advantage of that. So if you like this dig in with this sort of thing. And spend some time and look at the reference materials that we've recommended in the videos, that lay out our recommended books and articles in this area. And you'll find that you'll have a lot of fun playing with, and learning and being good at packet filtering, and also help you find a job. So I hope you enjoyed the video. We'll see you on the next one.