The Domain Name System (DNS) is one of the cornerstones of the Internet — it translates human-friendly domain names (e.g., example.com) into IP addresses (e.g., 192.168.1.1).
DNS security is therefore a critical component of network communication protection. A compromise of DNS can lead to phishing attacks, traffic hijacking, sabotage, or loss of customer trust.
What is the Domain Name System (DNS)?
DNS is often called “the phonebook of the Internet”. It converts domain names into IP addresses.
Every DNS query takes place before a website is loaded — which is why manipulating DNS responses can have severe security consequences.
By taking control of DNS responses, an attacker can redirect users to a fake website that looks identical to the legitimate one.
Common Threats to DNS
- DNS Spoofing / DNS Hijacking – the attacker impersonates a legitimate DNS server and redirects users to malicious sites.
- DNS Cache Poisoning – injecting false DNS records into a resolver’s cache to misdirect future queries.
- DDoS Attacks against DNS – flooding DNS servers with traffic to make services unavailable.
- DNS Tunneling – using DNS queries to exfiltrate data or communicate with Command & Control (C2) servers.
How to Secure the DNS System
- DNSSEC (DNS Security Extensions) – provides cryptographic assurance of the integrity and authenticity of DNS data.
- DNS Traffic Monitoring – detect anomalies and unusual queries that may indicate infection or data tunneling.
- DNS Filtering – block known malicious domains (e.g., using Quad9, Cloudflare Gateway, Cisco Umbrella, NextDNS).
- Zone Transfer Restrictions – allow DNS zone replication only to trusted servers.
- Encrypted DNS Queries – implement DNS-over-HTTPS (DoH) or DNS-over-TLS (DoT) to protect user privacy.
DNS Security Best Practices
- Keep DNS software up to date (BIND, Unbound, PowerDNS, etc.) and apply security patches promptly.
- Segment public-facing and internal DNS servers.
- Enable comprehensive logging and analyse DNS queries for incident investigation.
- Implement redundancy – run multiple DNS servers in different geographic locations.
- Use external validation tools such as Zonemaster or DNSViz to verify DNSSEC configuration and overall health.
Example of a Secure DNS Infrastructure
| Layer | Mechanism | Example |
|---|---|---|
| Data Integrity | DNSSEC | Cryptographic RRSet signatures |
| Privacy | DoH / DoT | Cloudflare 1.1.1.1, Quad9 9.9.9.9 |
| Monitoring | SIEM / IDS | Splunk, Suricata |
| Filtering | Secure DNS Filter | Cisco Umbrella, NextDNS |
Get in Touch
I help organisations design and harden DNS infrastructure, implement DNSSEC, set up DNS anomaly monitoring, and deploy malicious-query filtering in line with ISO/IEC 27035 and NIST SP 800-81r2.
Email: biuro@wichran.pl
Phone: +48 515 601 621
Author: Piotr Wichrań – Court-appointed IT expert, IT/OT cybersecurity specialist, licensed private investigator
@Informatyka.Sledcza