Quad9 DNS

Quad9 provides public DNS resolution, translating domain names into the addresses devices need to reach internet services. Its security-focused service checks requested domains against threat intelligence from multiple sources and blocks those identified as malicious. This includes domains associated with malware and command-and-control activity, adding protection at the point where a device tries to make a connection. The free service suits households and organizations that want DNS-level threat filtering without managing their own block lists.

Privacy is also part of its stated service policy. Blocking depends on identifying a dangerous domain, so it cannot prevent every threat or replace other security measures. Its distinguishing feature is the use of combined threat intelligence within ordinary DNS requests.