DNS Hijacking for Dummies: Why Your API's Domain Name is a Target š
DNS Hijacking for Dummies: Why Your API’s Domain Name is a Target š
You’ve hardened your servers, implemented authentication, encrypted your database, and reviewed every line of code for vulnerabilities. Your API is a fortress. But what if an attacker could hijack your users’ traffic without ever touching your infrastructure? Welcome to the world of DNS hijackingāwhere the weakest link isn’t your server, but the system that directs users to it.
Understanding the Invisible Layer
Domain Name System (DNS) is the internet’s phonebook, translating human-readable domain names like api.yourcompany.com into IP addresses that computers understand. Every time a user connects to your API, their browser or application performs a DNS lookup to find where your service lives. This seemingly simple translation process is where attackers find their opening.
The reality is sobering. Recent research uncovered approximately 70,000 domains hijacked through compromised DNS servers in 2024, with attackers altering DNS records to redirect legitimate traffic to malicious destinations. In the first quarter of 2024 alone, there were 1.5 million DNS DDoS attacksāa number that continues to climb. For developers building APIs and web services, this isn’t just a theoretical concern; it’s a clear and present danger.
How Attackers Control Your Traffic Without Touching Your Servers
DNS hijacking works because attackers manipulate the translation process between domain names and IP addresses. Think of it as switching the street signs in a cityāpeople think they’re going to the bank, but the signs actually lead them to a counterfeit operation. Your actual bank hasn’t been robbed; the customers just never made it there.
The sophistication of DNS attacks has evolved considerably. In 2024, security researchers observed new levels of complexity, with attackers employing advanced techniques specifically designed to evade detection. These aren’t script kiddies running automated toolsāthey’re sophisticated operations targeting government agencies, technology companies, insurance providers, and infrastructure providers across multiple sectors.
Subdomain Takeover: The Forgotten Backdoor
One of the most common and dangerous vulnerabilities developers face is subdomain takeover. This attack occurs when your DNS configuration points to a service that no longer exists, creating what security researchers call a “dangling DNS” entry.
Here’s a typical scenario: Your development team creates staging.api.yourcompany.com and points it to an AWS S3 bucket or a Heroku app for testing. The project wraps up, the cloud resource gets deleted to save costs, but nobody remembers to remove the DNS CNAME record. That record continues to exist in your DNS zone, pointing to a resource that’s now available for anyone to claim.
An attacker discovers this dangling DNS entry, registers the same S3 bucket name or Heroku subdomain that your DNS record points to, and suddenly they control your subdomain. Users visiting staging.api.yourcompany.com are now interacting with the attacker’s infrastructure while seeing your legitimate domain name in their address bar.
The scope of this problem is alarming. A security investigation conducted between October 2024 and January 2025 discovered approximately 150 abandoned S3 buckets previously owned by major corporations and government agencies. These buckets, still referenced by outdated DNS records, received over 8 million requests during the research periodāeach one a potential victim of subdomain takeover.
Microsoft’s security documentation highlights that subdomain takeovers are “common, high-severity threats” for organizations that regularly create and delete resources. The attack surface grows with every microservice architecture, every staging environment, every abandoned prototype, and every cloud migration.
DNS Cache Poisoning: Corrupting the Translation Layer
DNS cache poisoning attacks target the DNS resolvers that cache lookup results to improve performance. When successful, an attacker injects false DNS information into a resolver’s cache, causing all subsequent users querying through that resolver to be redirected to attacker-controlled servers.
The attack exploits the stateless nature of DNS. When a DNS resolver queries an authoritative server, it accepts the response without strong verification mechanisms in traditional DNS implementations. An attacker who can predict the transaction ID and source port of a DNS query can inject a forged response that appears legitimate.
Modern DNS cache poisoning has evolved beyond simple packet forgery. Attackers now employ techniques like DNS tunneling to bypass network firewalls and exfiltrate data, turning DNS into a command-and-control channel. The “Savvy Seahorse” campaign identified in 2024 demonstrated novel DNS hijacking techniques used to create convincing fake investment platforms, redirecting victims to phishing sites that appeared entirely legitimate.
DNS Hijacking Through Compromised Accounts
Sometimes the attack doesn’t exploit a technical vulnerability at allāit exploits human access controls. If an attacker compromises the credentials to your domain registrar account or DNS management panel, they can directly modify your authoritative DNS records.
This attack vector became painfully evident when widespread DNS hijacking campaigns targeted multiple sectors including government, technology, and civilian aviation. The attackers altered DNS records at the authoritative level, redirecting traffic for legitimate domains to infrastructure under their control. Because the changes occurred at the DNS provider itself, no amount of server-side security could prevent the hijacking.
The damage from this type of attack extends far beyond a temporary outage. Attackers can intercept authentication credentials, API keys, sensitive data, and session tokens. They can serve malware to your users, phish for credentials using your trusted domain name, or conduct supply chain attacks by compromising your subdomains that other organizations depend on.
Why Your API is Particularly Vulnerable
APIs present unique DNS security challenges that traditional websites don’t face. While a hijacked website might be quickly noticed by human visitors, APIs often operate in the background, making detection significantly more difficult.
Modern application architectures compound these risks. Microservices architecture means dozens or hundreds of subdomains, each representing a potential attack vector. DevOps practices emphasize rapid deployment and teardown of resources, increasing the likelihood of dangling DNS records. Cloud-native applications frequently create temporary resources tied to DNS entries that may outlive the resources themselves.
Consider a mobile application that communicates with your API at api.yourcompany.com. If that DNS record is hijacked, the mobile app continues functioning normally from the user’s perspectiveāit just communicates with the attacker’s server instead of yours. The attacker receives every API request, every authentication token, every piece of user data, all while your servers remain perfectly secure and untouched.
Third-party integrations amplify the attack surface. Your API might integrate with payment processors, analytics platforms, authentication providers, or CDNs. Each integration typically involves subdomains pointing to third-party infrastructure. When those third-party relationships end or change, dangling DNS records can emerge.
According to recent data, only 24% of companies on the Forbes Global 2000 list have implemented registry locks for their domainsāa critical protection mechanism we’ll discuss shortly. This means the vast majority of major corporations remain vulnerable to DNS hijacking attacks.
Real-World Impact: Beyond Theoretical Threats
The consequences of DNS hijacking extend far beyond hypothetical scenarios. When attackers control your domain’s DNS, they effectively become you in the eyes of your users and systems.
Data Breach: Every API call containing authentication tokens, user credentials, personal information, or business data flows to attacker-controlled servers. The attackers can collect this information while transparently proxying requests to your actual servers, making detection extremely difficult.
Service Impersonation: Attackers can serve entirely fake responses to API requests, manipulating application behavior. For a financial API, this could mean false account balances. For a healthcare API, incorrect medication information. For an authentication API, approved logins for unauthorized users.
Supply Chain Compromise: If other organizations depend on your API, subdomain takeovers become supply chain attacks. A recent assessment emphasized that subdomain takeovers should be re-evaluated as supply chain threats, not merely configuration issues. When attackers control a subdomain that other services trust, they inherit that trust relationship.
Reputation Damage: Users and partners lose confidence in your security posture when your domain name serves malicious content or leaks their data. The fact that your actual infrastructure was never compromised offers little comfort to affected parties.
Regulatory Consequences: Data protection regulations like GDPR, CCPA, and HIPAA don’t distinguish between data breaches caused by server compromises versus DNS hijacking. Your legal and financial liability remains the same regardless of the attack vector.
Mitigation Strategies: Taking Back Control
Defending against DNS hijacking requires a layered approach addressing both technical controls and organizational processes. No single solution provides complete protection, but combining multiple defensive measures significantly reduces your risk.
Implementing DNSSEC
DNS Security Extensions (DNSSEC) add cryptographic signatures to DNS records, allowing resolvers to verify that responses haven’t been tampered with. When properly implemented, DNSSEC prevents DNS cache poisoning and man-in-the-middle attacks at the DNS layer.
DNSSEC works through a chain of trust. The DNS root is signed, and each level of the DNS hierarchy validates the signatures from the level above. When a resolver queries your domain, it can verify the entire chain of signatures from the root to your specific records.
Major top-level domains have migrated to DNSSEC, including .com, .net, and .edu, which transitioned to more secure algorithms in late 2023. Many country-code TLDs including .at, .br, .cz, .ch, .fr, .ie, .nl, and .ph have also completed their migrations.
Implementing DNSSEC requires:
Enable DNSSEC signing on your authoritative DNS server or through your DNS provider. Major providers like Cloudflare, Google Cloud DNS, and AWS Route 53 offer straightforward DNSSEC implementation.
Create DS records at your domain registrar. These Delegation Signer records establish the chain of trust between your registrar and your DNS zone.
Configure validation for your resolvers if you manage your own DNS infrastructure.
Monitor DNSSEC status regularly. Expired signatures or misconfigurations can make your domain unreachable.
The limitation of DNSSEC is that both your authoritative servers and the user’s resolver must support it. However, even partial deployment provides significant protection against cache poisoning attacks.
Registry Locks: The Ultimate Protection
Registry lock is a security feature that prevents any modifications to your domain’s DNS records without a multi-step verification process. Unlike standard DNS changes that can be made through your web interface, registry-locked domains require explicit authorizationāoften involving phone verification or other out-of-band authentication.
Registry lock protects against:
- Account compromise at your registrar
- Social engineering attacks against support staff
- Unauthorized transfers of your domain
- Malicious DNS modifications
When registry lock is enabled, even if an attacker compromises your registrar account credentials, they cannot modify DNS records, transfer the domain, or delete it without completing additional verification steps. This dramatically slows down attackers and provides time for detection and response.
The trade-off is reduced agility. Legitimate DNS changes for registry-locked domains require going through the manual verification process, which can take hours or days. For critical production domains, this trade-off is almost always worthwhile. For development domains requiring frequent changes, you might choose different protection mechanisms.
Despite its effectiveness, adoption remains low. The 2024 Domain Security Report found that only one in four major corporations have implemented registry locks. This represents a massive security gap in DNS protection.
Hunting and Eliminating Dangling DNS Records
Preventing subdomain takeover requires vigilant monitoring of your DNS infrastructure for dangling records. This is particularly challenging in modern development environments where infrastructure constantly changes.
Implement automated scanning: Use tools like Nuclei, SubOver, or can-i-take-over-xyz to regularly scan your DNS records for vulnerable configurations. Many of these tools can be integrated into CI/CD pipelines.
Maintain a DNS inventory: Document every subdomain, what it points to, who created it, and its business purpose. This inventory makes it easier to identify orphaned records.
Establish deletion workflows: When teams decommission cloud resources, make DNS cleanup a required step in the process. This might involve infrastructure-as-code templates that manage both cloud resources and corresponding DNS entries together.
Monitor for takeover attempts: Configure alerts for DNS changes, especially for subdomains you don’t actively use. Tools from AWS, Azure, and Google Cloud can alert you when DNS configurations point to nonexistent resources.
Claim your own dangling records: If you discover a vulnerable subdomain pointing to an available cloud resource, claim that resource yourself. This “defensive registration” prevents attackers from exploiting the vulnerability while you work on a proper fix.
The UK Government Security Group has published detailed guidance on detecting potential subdomain takeovers, emphasizing that CNAME records pointing to services that no longer respond represent high-priority security risks.
Access Controls and Authentication Hardening
Since many DNS hijacking attacks begin with compromised credentials, securing access to your DNS management systems is critical:
Multi-factor authentication: Require MFA for all accounts with DNS management privileges. Use hardware tokens or authenticator apps rather than SMS-based verification.
Principle of least privilege: Grant DNS modification rights only to personnel who need them. Consider separate accounts for viewing versus modifying DNS records.
Audit logging: Enable comprehensive logging of all DNS changes. Review logs regularly for unauthorized modifications.
Registrar security: Choose domain registrars with strong security practices. Review their authentication mechanisms, change approval processes, and incident response capabilities.
API key rotation: If you manage DNS programmatically, rotate API keys regularly and audit their usage.
Separation of duties: Require multiple approvals for DNS changes to critical production domains.
Monitoring and Detection
Even with preventive controls, you need mechanisms to detect DNS hijacking attempts quickly:
DNS monitoring services: Use third-party DNS monitoring that queries your domain from multiple global locations and alerts you to unexpected changes in DNS responses.
Certificate Transparency logs: Monitor CT logs for unexpected TLS certificates issued for your domains. Attackers often need certificates to conduct convincing phishing or man-in-the-middle attacks.
Subdomain enumeration: Regularly enumerate your public-facing subdomains to identify any that you don’t recognize or control.
Traffic analytics: Monitor traffic patterns to your services. Sudden drops might indicate DNS hijacking redirecting your users elsewhere.
WHOIS monitoring: Track changes to your domain’s WHOIS information, including name servers and registrar details.
Security headers: Implement HTTP Public Key Pinning (HPKP) or its successor, Certificate Transparency enforcement, to detect when users receive certificates you didn’t issue.
Building a DNS Security Culture
Technical controls are essential but insufficient. Organizational culture and processes must emphasize DNS security:
Include DNS in threat models: When designing new services or infrastructure, explicitly consider DNS-related attack vectors.
Security training: Ensure developers understand subdomain takeover risks and proper DNS hygiene. Make this part of security onboarding.
Incident response plans: Develop and test procedures for responding to DNS hijacking. Who has authority to contact the registrar? How do you communicate with users during an incident? What’s your process for verifying legitimate DNS changes?
Regular audits: Schedule quarterly reviews of DNS configurations. Check for dangling records, verify DNSSEC operation, confirm registry lock status, and validate access controls.
Change management: Implement formal change management for DNS modifications to production domains. Require documentation, approval, and verification.
Conclusion: DNS Security is Application Security
For too long, developers have treated DNS as infrastructure concernāsomething for the ops team to handle. But in modern application architectures where DNS vulnerabilities can compromise entire systems without touching a single line of your code, DNS security is application security.
The attacks are real, sophisticated, and increasing in frequency. With 70,000 compromised domains, millions of malicious DNS requests, and only 24% of major organizations implementing registry locks, the threat landscape is clear. Your API’s domain name is a target, and attackers know that DNS is often the path of least resistance.
The good news is that effective defenses exist. DNSSEC protects against cache poisoning. Registry locks prevent unauthorized changes. Vigilant monitoring catches dangling DNS records. Strong access controls limit attack vectors. None of these solutions is perfect alone, but together they create a robust defensive posture.
The first step is recognition: DNS security deserves the same attention you give to authentication, encryption, and input validation. The second step is action: audit your DNS infrastructure today, implement the protections we’ve discussed, and make DNS security part of your development workflow.
Your servers might be secure, but if an attacker controls where your users’ traffic flows, your security means nothing. Take control of your DNS before someone else does.
This article reflects current DNS security threats and mitigation strategies as of October 2025. DNS security is a rapidly evolving field, and organizations should stay informed about emerging threats and updated best practices.