What is DNS domain name hijacking and domain name pollution

1. The basic principle of DNS

DNS Domain name system domain name system; the cornerstone of Internet communication is IP, but there are many IP and it is difficult to remember, so we use domain names instead of IP to make it easier for people to remember; then real communication must be carried out with IP, so domain names need to be resolved into IP.

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The DNS domain name service is a tree structure, com/net/cn/... from the first-level domain name To multi-level domain names, a domain name is resolved from its own near domain name, and finally to IP.

It is operators who are responsible for building and maintaining domain name servers, especially the domain name servers of some small operators are not very stable, and sometimes domain name hijacking occurs.

two。 Domain name hijacking

The domain name server keeps the records of all the domain names-- IP. When the domain name server receives the query request, it will query the corresponding records in the cache and database, and then return the result data to the client.

If someone (hacker) maliciously modifies the contents of the record so that the domain name is resolved to the wrong IP address, then the domain name is resolved to the wrong IP (which may be a competitor's web page), this is domain name hijacking.

3. Domain name pollution

The computer of the user client sends it to the DNS server to query the domain name, and then the DNS server queries the data and there is a delay between returning the data to the user. If hacker uses this time to forge a dns result data to return to the user

The resolution obtained by the user is also wrong, which is called domain name pollution.

4. GFW carries out "legal" domain name pollution

GFW is called the Great Firewall: it is a system in China that automatically censors and filters the content of the Internet. For example, if there is a website in foreign and domestic countries that always spreads negative energy, we can let GFW pollute the domain name of this website and resolve the domain name to an incorrect ip, then the website will not be accessible.