By Tyler Miller and Zach Howe
The domain name system is used everyday when you get on the internet. It determines the IP address of the computer that the hostname corresponds to.
For example, www.google.com resolves the A-type record as the IP address 74.125.45.100. With the domain name system you don’t have to type in your web browser, http://74.125.45.100 to go to Google. (You still can if you want. But some websites are hosted on shared hosting which means multiple hosts resolve as the same IP address. In this case the host HTTP request header will determine which website you visit.)
A-type records resolve normal IPv4 addresses AAAA-type records resolve IPv6 addresses MX-type records resolve mail exchange servers. TXT-type records resolve plain text or a specific URL. CNAME-type records are aliases of other DNS records. PTR-type records are used to implement reverse DNS lookups.
DNS can be exploited or “spoofed.”
This is done by pointing a DNS record to an IP address which it should not correspond to. For example, you could point www.google.com to 127.0.0.1 so it would not load at all, since 127.0.0.1 is the loopback IP address.
The hosts file is often used to add arbitrary domain names and forward them to a specific IP address locally.
This is done to override DNS and use the local definition for the hostname.
There are thirteen root DNS servers for the internet which store every domain name there is in their database.
There are more than thirteen DNS servers in the world but they all mirror or replicate off of the root servers. This can explain why when you register a new domain they say it can take up to 48 for your domain to appear active.
Pros
Cons
Makes it easier to remember website addresses. Easier to remember computer names over your private LAN.
DNS can be spoofed and poisoned locally. Host files can be poisoned to disable a website from being viewed locally.