Security strategies for DNS: Identifying and minimizing points of attack

DNS (Domain Name System) is the backbone of modern digital communication—a central component of every network, whether internal within companies or global via the Internet. Every URL, every email address, every web service relies on DNS to resolve names into IP addresses. 

DNS (Domain Name System) is the backbone of modern digital communication—a central component of every network, whether internal within companies or global via the Internet. Every URL, every email address, every web service relies on DNS to resolve names into IP addresses.

But it is precisely this central role that makes DNS a popular target for attack: Anyone who compromises DNS can redirect traffic, sabotage services, spy on users, or take them completely offline. The difference between a well-secured DNS and an open gateway often determines digital stability and trustworthiness.

This article highlights three essential security strategies that protect DNS from manipulation, exploitation, and abuse:

- DNSSEC to ensure data integrity,

- DNS-over-TLS (DoT) and DNS-over-HTTPS (DoH) to protect confidentiality,

- and Response Policy Zones (RPZ) as a proactive defense tool against threats.

1. DNSSEC – Integrity and authenticity through digital signatures

What is DNSSEC?

DNSSEC (Domain Name System Security Extensions) was developed as an extension of the DNS protocol to ensure that DNS responses are authentic and unaltered from the authoritative server. This is achieved through a chain of cryptographic signatures that extend from the root through TLDs to the zone level.

Without DNSSEC, any actor – an attacker on the WLAN, a compromised DNS server, or a man-in-the-middle – can return manipulated DNS responses that point to fake servers. DNSSEC prevents this.

How does DNSSEC work?

Each DNS record is signed with a private key.

The public key of the zone is published via so-called DS entries in the parent zone.

The resolver can check whether the response is signed throughout and valid.

Challenges

Complexity in key management: Zones must be re-signed regularly and keys must be rotated securely.

Not all registrars and DNS providers fully support DNSSEC.

DNSSEC does not protect the communication itself – only the content. 

Best Practice 

 ✔ Sign zones, automate key rollovers 
 ✔ Configure resolvers to treat invalid or unsigned zones as potentially compromised 
 ✔ Combine DNSSEC with DoT/DoH to secure the transport path as well 

2. DNS-over-TLS (DoT) & DNS-over-HTTPS (DoH) – Protecting confidentiality

Why do we need encrypted DNS?

Traditional DNS is based on UDP and is transmitted in plain text, which means that every DNS query and response can be read, stored, or modified by every node in the network.

In an age where data protection and privacy are key concerns, unencrypted DNS is a significant weak point. Two protocol extensions have therefore been developed:

What is DoT?

Uses the TLS protocol via port 853

Similar to HTTPS, but specifically for DNS data

Easy to control and easy to integrate into firewalls and networks

What is DoH?

Uses HTTPS (port 443), DNS requests are treated like normal web requests

Provides maximum concealment in uncontrolled environments

Supported by Firefox, Chrome, Android, Apple, and many platforms

Security relevance

Prevents DNS leaks and eavesdropping on the network

Bypasses DNS censorship (e.g., in authoritarian states)

In combination with DNSSEC, this creates a complete protection path

3. Response Policy Zones (RPZ) – Threat defense at the DNS level

What is RPZ?

RPZ is an extension for recursive DNS resolvers that can be used to manipulate or block DNS responses in a targeted manner. The idea: If a domain is known to be associated with malware or phishing, the resolver can set it to NXDOMAIN to prevent access.

Possible uses

Blocking domains with a bad reputation

Redirecting known botnet domains to internal honeypots

Informing users about dangerous behavior

Source of threat data

Own blacklists (e.g., from SIEM systems)

Commercial threat intelligence feeds

Open source databases such as Spamhaus or SURBL

Advantages

Very fast response to known threats

Low latency, no additional software required on clients

Centrally controllable, even in large environments

4. Integration into a comprehensive security concept

DNSSEC, DoT/DoH, and RPZ are not competing tools, but complementary ones. Their combination offers comprehensive protection on three levels:

- Data integrity (DNSSEC)

- Confidentiality of transmission (DoT/DoH)

- Detection and defense against known threats (RPZ)

Supplemented by logging, monitoring, and role-based access control, this creates a robust DNS security architecture.

An experienced analyst would emphasize that these measures are necessary but not sufficient. Reality shows that:

- DNSSEC is underrepresented: According to ICANN, less than 15% of domains registered worldwide are DNSSEC-signed.

- DoH is sometimes blocked in companies because it makes monitoring difficult.

- RPZ only works as well as the threat data on which it is based.

The greatest weakness often lies not in the technology, but in a lack of awareness, lack of implementation, and organizational inertia. 

Conclusion

DNS security is not an optional bonus—it is an essential component of modern IT security. Anyone who compromises DNS can redirect attacks unnoticed, exfiltrate data, and permanently destabilize systems.

The strategies presented here—DNSSEC, DoT/DoH, and RPZ—work at different levels, complement each other perfectly, and can be implemented in any organization at a reasonable cost.

However, the key to success lies not only in technical implementation, but also in a security awareness that treats DNS for what it is: one of the last unsecured pillars of digital infrastructure – and at the same time one of the most powerful.