DNS – CompTIA Security+ SY0-401: 1.4

We rely on the DNS protocol for almost everything that we do on our networks. In this video, you’ll get an overview of the domain name services protocol and learn how it is used to convert names to IP addresses.

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Our Domain Name Services, or DNS servers, are very important in IPv4 and especially IPv6, because their job is to take a name and convert it to an IP address. So if you were to look at and you type into your web browser www.professormesser.com, behind the scenes, your browser asks a Domain Name Server somewhere that it knows about, hey, do you happen to know how to get there? I’ve no idea the IP address of this website. Do you happen to know what that is? Well, sure. Here’s your answer.

Obviously these are very, very important resources, very critical resources from a security perspective. First, if somebody takes down your DNS, they could essentially take down people’s access to your services. Because I don’t have a list of everybody’s IP address. I rely on my DNS server for that.

You also have to be careful that nobody gets access to your DNS server and changes the IP addresses in there. If somebody was to do that to my DNS server, they would type in Professor Messer and might end up at a different IP address, perhaps even one looked exactly like my website. And that is phishing. That’s a problem. You could ask people to put in their user name and password thinking they were putting into a real website and they were not.

Now that is something that does occur. It’s very rare to have somebody break into a DNS server, because security professionals understand how important that resource is and they tend to keep that very, very secure.

You also have to watch out just for plain old redirection. You don’t want somebody going to your site and suddenly ending up on a competitor’s site because they typed in your particular name and the DNS server was completely wrong. Somebody got in there and changed where people were going.

So Domain Name Services is incredibly useful. The way you would perhaps even look some of these up is to use the nslookup command. And if you use the nslookup of www.professormesser.com, it even tells you it goes out to my DNS server, which is That is Google’s DNS. And it says, here’s the answer. ProfessorMesser.com can be found at