DNS Hijacking

DNS hijacking (sometimes referred to as DNS redirection) is a type of malicious attack that overrides a computer’s TCP/IP settings to point it at a rogue DNS server, thereby invalidating the default DNS settings. In other words, when an attacker takes control of a computer to alter its DNS settings, so that it now points to a rogue DNS server, the process is referred to as DNS hijacking.

As we all know, the “Domain Name System (DNS)” is mainly responsible for translating a user friendly domain name such as “google.com” to its corresponding IP address “74.125.235.46”. Having a clear idea of DNS and its working can help you better understand what DNS hijacking is all about. If you are fairly new to the concept of DNS, I would recommend reading my previous post on How Domain Name System Works.

How DNS Hijacking Works?

As mentioned before, DNS is the one that is responsible for mapping the user friendly domain names to their corresponding IP addresses. This DNS server is owned and maintained by your Internet service provider (ISP) and many other private business organizations. By default, your computer is configured to use the DNS server from the ISP. In some cases, your computer may even be using the DNS services of other reputed organizations such as Google. In this case, you are said to be safe and everything seems to work normally.

But, imagine a situation where a hacker or a malware program gains unauthorized access to your computer and changes the DNS settings, so that your computer now uses one of the rogue DNS servers that is owned and maintained by the hacker. When this happens, the rogue DNS server may translate domain names of desirable websites (such as banks, search engines, social networking sites etc.) to IP addresses of malicious websites. As a result, when you type the URL of a website in the address bar, you may be taken to a fake website instead of the one you are intending for. Sometimes, this can put you in deep trouble!

What are the Dangers of DNS Hijacking?

The dangers of DNS hijacking can vary and depend on the intention behind the attack. Many ISPs such as “OpenDNS” and “Comcast” use DNS hijacking for introducing advertisements or collecting statistics. Even though this can cause no serious damage to the users, it is considered as a violation of RFC standards for DNS responses.

Other dangers of DNS hijacking include the following attacks:

Pharming: This is a kind of attack where a website’s traffic is redirected to another website that is a fake one. For example, when a user tries to visit a social networking website such as Facebook.com he may be redirected to another website that is filled with pop-ups and advertisements. This is often done by hackers in order to generate advertising revenue.

Phishing: This is a kind of attack where users are redirected to a malicious website whose design (look and feel) matches exactly with that of the original one. For example, when a user tries to log in to his bank account, he may be redirected to a malicious website that steals his login details.

How to Prevent DNS Hijacking?

In most cases, attackers make use of malware programs such as a trojan horse to carry out DNS hijacking. These DNS hijacking trojans are often distributed as video and audio codecs, video downloaders, YoTube downloaders or as other free utilities. So, in order to stay protected, it is recommended to stay away from untrusted websites that offer free downloads. The DNSChanger trojan is an example of one such malware that hijacked the DNS settings of over 4 million computers to drive a profit of about 14 million USD through fraudulent advertising revenue.

Also, it is necessary to change the default password of your router, so that it would not be possible for the attacker to modify your router settings using the default password that came with the factory setting. 

Installing a good antivirus program and keeping it up-to-date can offer a great deal of protection to your computer against any such attacks.

What if you are already a victim of DNS hijacking?

If you suspect that your computer is infected with a malware program such as DNSChanger, you need not panic. It is fairly simple and easy to recover from the damage caused by such programs. All you have to do is, just verify your current DNS settings to make sure that you are not using any of those DNS IPs that are blacklisted. Otherwise re-configure your DNS settings as per the guidelines of your ISP.

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How Domain Name System (DNS) Works

In the world of Internet and the area of computer networks, you will often come across the term Domain Name System or Domain Name Service which is simply referred to as DNS. The working of DNS forms one of the basic concepts of computer networks whose understanding is very much essential especially if you are planning to get into the field of ethical hacking or network security.

In this post, I will try to explain how Domain Name System works in a very simple and easy to follow manner so that even the readers who do not have any prior knowledge of computer networks should be able to understand the concept.

What is a Domain Name System?

A “Domain Name System” or “Domain Name Service” is a computer network protocol whose job is to map a user friendly domain name such as “Gohacking.com” to its corresponding IP address like “173.245.61.120”.

Every computer on the Internet, be it a web server, home computer or any other network device has a unique IP address allotted to it. This IP address is used to establish connections between the server and the client in order to initiate the transfer of data. Whether you are trying to access a website or sending an email, the DNS plays a very important role here.

For example, when you type “www.google.com” on your browser’s address bar, your computer will make use of the DNS server to fetch the IP address of Google’s server that is “74.125.236.37”. After obtaining the IP address, your computer will then establish a connection with the server only after which you see the Google’s home page loading on your browser. The whole process is called DNS Resolution.

With millions of websites on the Internet, it is impossible for people to remember the IP address of every website in order to access it. Therefore, the concept of domain name was introduced so that every website can be identified by its unique name which makes it easy for people to remember. However, the IP address is still used as the base for internal communication by network devices. This is where the DNS comes in to action that works by resolving the user friendly domain name to its corresponding machine friendly IP address.

In simple words, domain names are for humans while IP addresses are for network devices. The “Domain Name System” is a protocol to establish a link between the two. Hence, it is not a surprise that you can even load a website by directly typing its IP address instead of the domain name in the browser’s address bar (give it a try)!

Types of DNS Servers and their Role:

The Domain Name System (DNS) is a distributed database that resides on multiple computers on the Internet in a hierarchical manner. They include the following types:

Root Name Servers:

The root servers represent the top level of the DNS hierarchy. These are the DNS servers that contain the complete database of domain names and their corresponding IP addresses. Currently, there are 13 root servers distributed globally which are named using the letters A,B,C and so on up to M.

Local Name Servers:

Local servers represent the most lower level DNS servers that are owned and maintained by many business organizations and Internet Service providers (ISPs). These local servers are able to resolve frequently used domain names into their corresponding IP addresses by caching the recent information. This cache is updated and refreshed on a regular basis.

How DNS Server Works?

Whenever you type a URL such as “http://basichackingtips.blogspot.in” on your browser’s address bar, your computer will send a request to the local name server to resolve the domain name into its corresponding IP address. This request is often referred to as a DNS query. The local name server will receive the query to find out whether it contains the matching name and IP address in its database. If found, the corresponding IP address (response) is returned. If not, the query is automatically passed on to another server that is in the next higher level of DNS hierarchy. This process continues until the query reaches the server that contains the matching name and IP address. The IP address (response) then flows back the chain in the reverse order to your computer.

In rare cases where none of the lower level DNS servers contain the record for a given domain name, the DNS query eventually reaches one of the root name server to obtain the response.

FAQs about Domain Name System:

Here is a list of some of the FAQs about DNS:

How does a “root name server” obtain the information about new domains?

Whenever a new domain name is created or an existing one is updated, it is the responsibility of the domain registrar to publish the details and register it with the root name server. Only after this, the information can move down the DNS hierarchy and get updated on the lower level DNS servers.

What is DNS propagation?

Whenever a new domain name is registered or an existing one is updated, the information about the domain must get updated on all the major DNS servers so that the domain can be reached from all parts of the globe. This is called DNS propagation and the whole process can take anywhere from 24 to 72 hours to get completed.

How often the DNS servers are updated to refresh the cache?

There is no specific rule that defines the rate at which DNS servers should be updated. It usually depends on the organization such as the ISP that maintains the server. Most DNS servers are updated on an hourly basis while some may update their databases on a daily basis.

I hope you have now understood the working of DNS in a very convincing manner. Pass your comments and share your opinion

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