DNS Security: Poisoning, Hijacking, and Hardening That Actually Sticks

DNS translates names into addresses. Attackers abuse it to redirect users to phishing sites, bypass security controls, and exfiltrate data in plain sight. Defending DNS is less about exotic zero-days and more about architecture, monitoring, and closing obvious gaps.

Cache Poisoning and Resolver Trust

Resolvers that accept spoofed answers can serve wrong IP addresses to clients until caches expire. Use DNSSEC where your zones and providers support it, and prefer trusted recursive resolvers with strong anti-spoofing behavior for client and server workloads.

Domain and Registrar Hygiene

Domain hijacking via stolen registrar credentials or expired domains bypasses most network controls. Lock domains, use registry lock where available, enforce 2FA on registrar accounts, and monitor WHOIS and certificate transparency for unexpected changes.

Encrypted DNS: DNS over HTTPS / TLS

DoH and DoT protect query privacy on the wire and reduce some on-path manipulation, but they also shift policy to which resolver you trust. Corporate environments should explicitly choose resolvers and logging policies instead of defaulting to browser or OS choices.

Monitoring and Threat Intel

Log query patterns for rare resolutions, newly registered domains contacted by endpoints, and DNS tunneling indicators. Correlate DNS telemetry with EDR and firewall data for faster triage.

Conclusion

DNS security is defense in depth: secure zones, secure resolvers, secure accounts, and visibility into what your systems resolve every day.