The hosts file is a file in Linux systems responsible for fast resolution between IP addresses and domain names, saved in ASCII format in the “/etc” directory with the filename “hosts”. The hosts file contains mappings between IP addresses and hostnames, including aliases for hostnames. Without a domain name server, all network programs on the system resolve IP addresses corresponding to hostnames by querying this file; otherwise, DNS services are required. Commonly used domain names and IP address mappings can be added to the hosts file for quick and convenient access. Malicious modifications to the hosts file can cause services to become unavailable.
If the /etc/hosts file has been illegally modified, carefully inspect the host environment to determine if it has been compromised and change the host user passwords.