DNS (Domain Name System)
DNS, the Domain Name System, is the internet's address book that turns names people can read, such as example.co.uk, into the number addresses computers use. DNS is not one of the five Cyber Essentials controls. It appears in the Cyber Essentials Plus test specification, where DNS entries can define which addresses are scanned.
- Term
- DNS
- Also known as
- Domain Name System, DNS record, DNS filtering
- Category
- Networks and firewalls
- Requirement area
- Scheme vocabulary
- Questions
- None directly
- Reviewed against
- Requirements v3.3
What does the term DNS mean in Cyber Essentials?
DNS, the Domain Name System, is the internet's address book that turns names people can read, such as example.co.uk, into the number addresses computers use.
How does DNS apply to Cyber Essentials?
In plain terms
People remember names and computers use numbers. When you type a web address, your device asks a DNS server which IP address belongs to that name, a bit like looking up a phone number in a directory. Your organisation's DNS records say where your website and email live.
What Cyber Essentials asks
The requirements document and the 2026 question set do not set any DNS requirement. DNS appears in the Cyber Essentials Plus test specification, in test case 1: "Where dynamic IP addresses are in use for an Internet connection, the scope may be defined in terms of appropriate DNS entries." So if your broadband address changes, the assessor can scan the name that points to it rather than a fixed number.
Some firewalls and security products offer DNS filtering, which blocks lookups for known malicious sites. That can be useful, but it is not one of the scheme's malware protection options. The malware control lists anti-malware software, which must "prevent connections to malicious websites over the internet", and application allow listing.
What an assessor looks for
- Accurate DNS names or addresses for every internet connection and cloud server before the external scan.
- Records for a server or service you forgot about. If the address behind it is still yours, it is in the scan.
See Test 1: the external vulnerability scan. Related: static IP address, internet-facing.
Related terms
- IP addressAn IP address is the number that identifies a device or internet connection on a network, so that traffic can be delivered to the right place.
- Static IP addressA static IP address is a public internet address that stays the same over time, unlike a dynamic address that your broadband provider can change without notice.
- Internet-facingInternet-facing describes a device or service that anyone on the internet can reach and try to connect to, such as a website, a VPN login page or an email server.
- External vulnerability scanAn external vulnerability scan is an automated check, run from the internet, that looks at every public address your organisation uses for services an attacker could reach and weaknesses in them.
- FirewallA firewall is a device or piece of software that sits between your computers and the internet and decides, using a set of rules, which traffic is allowed through.
- Firewall ruleA firewall rule is a single instruction on a firewall that says which traffic to allow or block, based on where it comes from, where it is going and what type it is.
Frequently asked questions
DNS, the Domain Name System, is the internet's address book that turns names people can read, such as example.co.uk, into the number addresses computers use.
Would you pass the 2026 question set?
Answer 24 yes or no questions, built by the assessors who mark Cyber Essentials, and get a readiness score in about five minutes, with any auto-fail questions you miss flagged first in your results.