Edit hosts file
The hosts file is a system file on a device that lets you map specific domain names to an IP address. If you want to add new entries to the hosts file, you’ll need the IP address of the server that you want to map a hostname to.
The hosts file lets you override DNS entries for any domain name. There are lists of common ad networks and tracking servers available online which you can use to keep an up-to-date list of sites to block. Blocking is achieved by setting the IP address of the ad networks to a loopback address like 127.0.0.1 which will not return anything. There are lists of common ad networks and tracking servers available online which you can use to keep an up-to-date list of sites to block.
If your device is infected with malware, then your hosts file may be compromised to included unknown entries for known
domain names. That is NOT the IP address of your bank! This type of DNS attack is known as DNS pharming, and checking
hosts file can uncover potential infection.
Open the Terminal application. (Click on the Finder icon and then go to Applications → Utilities)
In the terminal, give the command
sudo nano /private/etc/hosts
Enter your administrator password after running the command
Add as many entries as needed