DNS Hijacking: How It Works and How to Detect It

DNS hijacking is the redirection of DNS queries or the modification of DNS records so that a domain resolves to an IP address the attacker controls instead of the legitimate one. It is one of the most effective attack vectors available because it is invisible to the end user and often to the domain owner as well.

When DNS is hijacked, users who type your domain into their browser are silently sent to a different server. That server can serve a pixel-perfect copy of your website, harvest credentials, intercept email, or distribute malware. The URL bar still shows your domain name. There is no browser warning unless the attacker fails to obtain a valid SSL certificate.

Types of DNS Hijacking

DNS hijacking is an umbrella term that covers several distinct attack methods. Each targets a different point in the DNS resolution chain.

Registrar-Level Hijacking

The attacker gains access to your domain registrar account and changes the nameserver records. This gives them complete control over your DNS zone. They can point your domain to any server they choose and create any records they want.

This is the most damaging type of hijacking because it is authoritative. Every resolver in the world will eventually see the attacker's records as the legitimate ones.

How it happens: Credential theft (phishing, password reuse, credential stuffing), social engineering of registrar support staff, or exploitation of registrar platform vulnerabilities.

DNS Provider Account Compromise

If you use a third-party DNS provider (separate from your registrar), compromising that account gives the attacker control over your zone records without needing registrar access. They can modify A records, MX records, TXT records, and anything else in the zone.

How it happens: Similar to registrar compromise: stolen credentials, insufficient access controls, compromised API keys.

Man-in-the-Middle (On-Path) Attacks

The attacker intercepts DNS queries between the user and the recursive resolver, or between the resolver and the authoritative server. They inject forged responses that point to the attacker's IP.

How it happens: Network-level access (compromised router, malicious WiFi hotspot, ISP-level interception). This attack targets specific users or networks rather than affecting all users globally.

DNS Cache Poisoning

The attacker sends forged DNS responses to a recursive resolver, tricking it into caching an incorrect record. Once the resolver's cache is poisoned, every user who queries that resolver gets the wrong answer until the cache expires.

How it happens: The attacker exploits weaknesses in the DNS protocol (predictable transaction IDs, lack of source port randomization) to inject responses that the resolver accepts as legitimate.

Rogue DNS Server

The attacker configures a device (typically through malware or a compromised router) to use a DNS server they control. All queries from that device are resolved by the attacker, who can return any IP they choose for any domain.

How it happens: Malware that changes DNS settings, compromised home routers with default credentials, DHCP attacks on local networks.

BGP Hijacking Affecting DNS

By advertising false BGP routes, an attacker can redirect traffic destined for DNS server IP addresses through their own network. This allows them to intercept and modify DNS queries and responses at the network routing level.

How it happens: Exploitation of BGP's trust-based design. Requires access to a network capable of announcing BGP routes, but has been observed in real attacks.

How DNS Hijacking Attacks Play Out

Understanding the attack sequence helps clarify why these attacks are so dangerous.

Real-World Examples

DNS hijacking is not theoretical. It has been used in major attacks.

How to Detect DNS Hijacking

Detection is the critical link between an attack happening and being able to respond. DNS hijacking is designed to be invisible, so passive observation rarely catches it.

Continuous DNS Monitoring

The most effective detection method is automated monitoring that regularly queries your DNS records from multiple geographic locations and compares results against known-good baselines. Any deviation triggers an immediate alert.

Monitoring should cover:

• All record types (not just A records)
• Multiple resolver locations (to detect poisoning of specific resolvers)
• Historical comparison (to detect gradual changes)

Certificate Transparency Logs

Monitoring Certificate Transparency (CT) logs for your domain can reveal when someone obtains an SSL certificate for your domain. If you did not request a certificate, it may indicate that an attacker has hijacked your DNS and used DNS validation to issue one.

DNSSEC Validation Failures

If you have DNSSEC enabled, hijacking attempts that modify records will cause validation failures for DNSSEC-aware resolvers. Monitoring for DNSSEC validation errors can indicate an attack in progress.

Anomalous Traffic Patterns

A sudden drop in legitimate traffic can indicate that users are being redirected elsewhere. If your server logs show a significant decrease in requests while users report they can access your site "normally," your domain may be resolving to a different server.

Prevention Measures

DNSSEC Is Essential but Not Sufficient

DNSSEC (Domain Name System Security Extensions) adds cryptographic signatures to DNS records. Resolvers that validate DNSSEC can detect forged responses, which protects against cache poisoning and man-in-the-middle attacks.

However, DNSSEC does not protect against registrar-level hijacking. If the attacker changes your nameservers at the registrar, they can set up their own DNSSEC-signed zone. DNSSEC also does not help if the validating resolver itself is compromised or if the user's resolver does not support DNSSEC validation.

CAA Records Limit Certificate Issuance

Certificate Authority Authorization (CAA) records specify which certificate authorities are allowed to issue certificates for your domain. This does not prevent DNS hijacking, but it can prevent an attacker from easily obtaining a valid SSL certificate if they hijack your DNS but do not modify the CAA record (or if the CA checks the legitimate CAA record).

Registry Lock Is Underused

Registry lock requires out-of-band verification (phone call, multi-step authentication) before nameserver or registrar changes can be made at the registry level. This is the strongest defense against registrar-level hijacking and social engineering attacks. Despite its effectiveness, most domains do not use it because it requires manual interaction and sometimes a premium fee.

Building a Defense-in-Depth Strategy

No single measure prevents all types of DNS hijacking. An effective defense combines multiple layers.

DNS hijacking remains one of the most potent attack vectors because it subverts the fundamental trust model of the internet. Users trust that a domain resolves to the right place. Attackers exploit that trust. The defense is layered: sign your records, lock your domain, secure your accounts, and monitor continuously.