What is a DNS server?

Linh Le

We explain what a DNS server is, how it works and how to avoid DNS hijacking

Without DNS servers, the internet wouldn’t work properly. A DNS server is a crucial part of the DNS (domain name system) infrastructure. It stores IP addresses and their hostnames and this data is used to resolve queries by users wanting to access a particular website, device or any other networked system that uses an IP address. Also known as nameservers, DNS servers are very handy indeed.

When is a DNS server used?

When a user types in a host address or URL into their address bar in a browser, the DNS resolver will contact a DNS server to find the IP address connected to the hostname and take this back to the user, so they can look at the website or device they want to access.

If a DNS resolver can’t find the information they need, it will then move along to the next DNS server in the DNS server hierarchy until it finds the data needed to resolve an address.

How is the DNS server set up?

An ISP would normally set up their own DNS server. As well as that, the router used in the home or office will also be used by computers attached to them as a DNS server for URL queries. Router act as gatekeepers, forwarding on requests to an ISP’s DNS servers.

Are some DNS servers faster than others?

How fast a DNS is and how fast queries resolve depends a lot on where the DNS server resides. The majority of ISPs distribute their DNS servers around the world, so that wherever you are located, you’ll be close to one that can power your website. But you may be one of the unfortunate people who lives further away from their server and so you and visitors to your site will experience a slower response.

DNS speed is also affected by how far the visitor is from the DNS. If they’re close, they too will experience a faster service. If they live on the other side of the world, then they will experience a slower service, although it will be barely noticeable.

If you’ve visited a webpage before, the DNS lookup may be faster too, because the hostname and IP address have already been resolved and will be stored locally so it doesn’t have to search for the connection when you type in the domain name.

One solution to this problem (although not affecting the DNS directly) is to use a content delivery network (CDN) that will deliver the content faster when the query resolves. A CDN puts your content into a location local to the visitor, so even if the DNS takes longer to resolve, the content (i.e. pictures and assets that build the website) are delivered to the user’s computer faster because it doesn’t have as far to travel.

DNS server security concerns

Sometimes, DNS servers can be hijacked by hackers, leading unsuspecting victims to fake websites that appear to be the site you’re trying to reach, but the IP address has been changed to appear as though it’s the genuine site.

To avoid falling victim to such scams, you should ensure your antivirus and malware detection tools are up to date and if you see an ‘invalid certificate’ warning message, it’s a good idea not to head to the website, especially if it’s asking for sensitive information.

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Source : http://www.itpro.co.uk