How we access websites on internet and how hacker hack can your computer by DNS spoofing

How we access websites on internet

Everything which is connected on internet is assigned an IP address.The DNS resolves domain names to IP addresses.
 
For example:
Basically the end dot in for example yahoo.com represents the root of internet name space. When we search for yahoo.com on web browser then:
The DNS server search through its database  to find  matching  IP address to that domain name.When it is found it will resolve that domain name to  IP address  of  yahoo.com website then your computer will be able to gain access to yahoo server and retrieve yahoo webpage.

 
If computer doesn’t find IP address on its own cache memory then:
1)It will  send query to next level known as ISP(internet service provider) Resolver. The ISP will check its own  cache memory to find and if still it doesn’t find it there then

2)It will send query to next level which is the Root server.Root server or top most server contain 13 sets strategically placed around the world.Each set of root server has their own unique IP address.It is organized by 12 different organizations.

 

3)Now root server will send ISP Resolver to TLD(top  level domain) server which stores information for top level domains such as .com,. net, .org etc

4)TLD will direct you to authoritative name server which is responsible for knowing everything about domain including  IP address.Final authority tell ISP the IP address of yahoo.com.Now ISP will give your computer the IP address of yahoo.com and you can retrieve the webpage

NOTE: once the ISP i.e resolver receive the address it will store it in it’s  cache memory.

 Q)How did the TLD server came to know which authoritative name servers to use 
Ans:With the help of  domain registrar i.e when the domain is purchased.

How hacker  can hack your computer

DNS spoofing is an attack in which the hacker modifies the IP address assigned to a Website to the IP address of the hacker's computer .As a result when a user sends request to  a website ,DNS servers convert the host name to the incorrect IP address so changing the IP address directs the user to hacker's computer and the hacker can send malicious code to the user's computer because user is assuming is assuming that the data is from a trusted source.