According to Quad9’s annual reports, the service blocks millions of malicious queries daily. For a home user, this is a free, zero-configuration firewall layer.
3.3.3.3 is a public DNS resolver IP address — a server you can point your device or network to for domain name lookups (translating domain names like example.com into IP addresses). dns 3.3.3.3
Using 3.3.3.3 presents a unique risk/reward profile: According to Quad9’s annual reports, the service blocks
Because 3.3.3.3 was historically unrouted on the public internet, it became a favorite "dummy" address for:Setting up virtual tunnels.Testing firewall rules.Configuring guest Wi-Fi captive portals. The Danger of Using Non-Public DNS According to Quad9’s annual reports
It is part of the AWS global network and is often assigned as an Elastic IP (EIP) for various cloud services.