Glossary
DNS
Domain Name System — a foundational internet infrastructure that translates domain names into IP addresses, classified as critical infrastructure under NIS 2.
The DNS (Domain Name System) is a foundational internet infrastructure that acts as a global "directory", translating human-readable domain names (e.g. my-portal.com) into server IP addresses. DNS resolution service providers are by default subject to the highest security tier of the NIS 2 directive.
How it works, simplified
When a user types a web address into their browser:
- The browser queries a DNS resolver (often run by the ISP or a third-party service).
- The resolver consults the root DNS servers, then the relevant domain's name servers.
- The IP address of the server hosting the site is returned.
- The connection is established with the correct server.
This process happens in a few milliseconds and is invisible to the user.
Why DNS is critical for NIS 2
An attack against DNS servers can make thousands of sites and services unreachable at once. This is why NIS 2 places DNS service providers in Annex I (highly critical sectors) and subjects them to the strictest obligations, regardless of size.
Types of DNS providers in scope
- Public recursive DNS resolver providers (e.g. Cloudflare 1.1.1.1, Google 8.8.8.8)
- Operators of authoritative name servers for critical domains
- ISPs running resolvers for their subscribers