In the early days of the Internet, all the domain names (nodes) it had been listed in just one file, the host file. The host file has been demoted to just a way to redirect an IP address to a specific domain name, which the operating system checks first before querying the DNS servers. Maintaining DNS servers is a cost to Internet Service Providers (ISP) that is why it is the last aspect of their service that they usually take care of.”]
Source: https://hackercombat.com/how-to-deal-with-dns-vulnerabilities/