What are DNS Misconfigurations? And How to Prevent Them

When was the last time you looked at your DNS settings? For many organizations, DNS is an essential part of their infrastructure. It quietly translates domain names into IP addresses, and it is all good until something goes wrong.

Misconfigurations in DNS are a goldmine for attackers and a nightmare for security teams, leading to data breaches, downtime, and exploitation. Recent research reveals the scale of the problem: 72% of organizations experienced a DNS attack in the past year, with nearly half of those involving DNS hijacking—where attackers manipulate DNS queries to redirect users to malicious servers. Another study revealed that over 4% of domains implementing DNSSEC showed critical misconfigurations, with the majority of them failing to resolve properly.

With such widespread risks and vulnerabilities stemming from DNS misconfigurations, security professionals and researchers have a critical role to play. Identifying these security misconfigurations early is essential to strengthening defenses and minimizing exposure to threats. Let’s explore these misconfigurations, why they’re dangerous, and how to spot them effectively.

Top 10 DNS Servers Misconfigurations

DNS, or Domain Name System, is the internet’s address book. It directs users to the right servers so communication runs smoothly. But when DNS settings are misconfigured they create vulnerabilities that attackers can exploit to get access, disrupt services, or steal sensitive data. Attackers often exploit misconfigured DNS records to take control of domains and get network access. They can redirect users to a malicious server by exploiting these DNS misconfigurations.

Here are the top 10 most common DNS misconfigurations to watch out for:

Open Resolvers: An open resolver allows anyone on the internet to query your DNS server. While this may seem harmless, attackers often abuse open resolvers for amplification in Distributed Denial of Service (DDoS) attacks. These attacks can take down a target and cause widespread outages.
Exposed Zone Transfers: Zone transfers are supposed to sync DNS records between servers but should only happen between trusted machines. If not restricted, anyone can request a zone transfer and get access to your DNS data, including internal subdomains and IPs. This misconfiguration is handing over your internal network map to the attackers.
Not Implementing DNSSEC: DNS Security Extensions (DNSSEC) protects DNS records from tampering. Without DNSSEC attackers can spoof DNS responses and redirect users to malicious sites. Worse, misconfigured DNSSEC can introduce its own set of vulnerabilities.
Stale or Orphaned DNS Records: Over time DNS records can become outdated, pointing to servers or IPs that no longer exist. These stale records are a security risk as attackers can take over the old resources and use them for phishing, malware delivery or other malicious activities.
Misconfigured TTL (Time to Live) Settings: TTL settings determine how long DNS records are cached. If they’re too short your DNS servers will get flooded with repeated queries. If they’re too long outdated records will linger and cause disruptions or misroute traffic.
Reverse DNS Issues: Lack of proper PTR (pointer) records will disrupt reverse DNS lookups which are often used to verify email senders or network trustworthiness. This can cause deliverability issues or make your network look suspicious to external systems.
Wildcard DNS Records Gone Wrong: Wildcard records allow non-existent subdomains to resolve to a specific address. Misusing this feature can create phishing opportunities by making it easy for attackers to spoof your domain with seemingly legitimate subdomains.
Incorrect MX Records: Mail Exchange (MX) records determine where your email traffic goes. Misconfigurations can cause lost emails, misrouted messages, or even open the door to email interception.
Split-Horizon DNS Missteps: Split-horizon DNS serves different responses depending on whether the requester is internal or external. When not configured properly, sensitive internal records can be leaked to external users or users will get inconsistent results.
Unsecured Authoritative Name Servers: Outdated or misassigned authoritative name servers will send queries to the wrong servers. This is often the cause of service disruptions or DNS hijacking.

Why DNS Queries Misconfigurations Matter

DNS is the foundation of the internet. When it’s broken everything else connected to it is broken too. Attackers target misconfigured DNS settings especially those that don’t associate an IP to DNS records because they can bypass traditional security measures.

For security teams and researchers:

Data Leakage: Exposed DNS records will give attackers info about your infrastructure.
Service Downtime: Misconfigured DNS will cause outages that will disrupt business-critical functions.
Reputation Damage: If users are redirected to phishing sites due to DNS hijack it will erode trust in your organization.

DNS Server Configuration Best Practices

Configuring a DNS server requires planning and attention to detail to get optimal performance, security, and reliability. Here are some best practices:

Use an External DNS Service: Use a reputable external DNS service like Google DNS or Cloudflare DNS. These services will add an extra layer of security and redundancy to your DNS infrastructure protect it from attacks and ensure high availability.
Clean (Scavenge) DNS Zones: Over time DNS records will become outdated or stale and will cause DNS pollution and resolution issues. Review and remove stale DNS records regularly to keep your DNS zone clean and healthy.
Set TTL to 60 when changing Hosts: When changing DNS records, set the TTL (Time-To-Live) to 60 to propagate changes faster. This will minimize the impact of DNS caching and reflect changes across the network quickly.
IP and Reverse Lookup Configuration: Verify IP addresses are correctly configured and reverse lookup settings are set up properly. This will prevent DNS resolution issues and DNS queries will be resolved correctly.
Attach DNS to Router or DHCP Server for Client Systems: Attaching DNS to the router or DHCP server will allow client systems to access the DNS server and resolve domain names. This will improve DNS availability and reliability for end users.

DNS Zone Transfer Security

DNS zone transfer is a part of DNS management but can be a security risk if not configured properly. Here are some best practices:

Use TSIG for Authentication: Use TSIG to authenticate zone transfers and prevent unauthorized access to DNS data. TSIG uses shared secret keys to ensure that only authorized servers can do zone transfers.
Review and Audit DNS Configurations Regularly: Review and audit DNS configurations regularly to ensure zone transfers are configured properly and securely. This will help you identify and address potential vulnerabilities before they can be exploited.
Limit Zone Transfers to Authorized Servers: Limit zone transfers to only authorized servers to prevent unauthorized access to DNS data. You can do this by specifying the IP addresses of trusted servers in the DNS configuration.
Use Secure Protocols for Zone Transfers: Use secure protocols like TCP or SSL/TLS for zone transfers to prevent eavesdropping and tampering. Secure protocols will ensure DNS data is transmitted securely between servers.

DNS Records Management

DNS records management is part of DNS management. Here are some best practices:

Use a DNS Management Tool: Use a DNS management tool like a DNS editor or a DNS manager to simplify DNS records management. These tools will provide a user-friendly interface to create, update, and delete DNS records.
Keep DNS Records Current: Review and update DNS records regularly to ensure they are accurate and current. This will prevent DNS resolution issues and users can access websites and applications without interruption.
Use DNS Record Templates: Use DNS record templates to simplify creating new DNS records. Templates will provide a standard format for common DNS record types and reduce the chance of errors.
Document DNS Records: Document DNS records to ensure they are properly configured and for troubleshooting. Keeping detailed documentation will help you track changes and have a reference for future updates.

DNS Misconfiguration Errors

DNS misconfiguration errors can cause DNS resolution issues and security vulnerabilities. Here are some common DNS misconfiguration errors:

Incorrect DNS Records: Incorrect DNS records will cause DNS resolution issues and users can’t access websites and applications. Ensure DNS records are correctly configured to avoid downtime.
Misconfigured DNS Servers: Misconfigured DNS servers will cause DNS resolution issues and users can’t access websites and applications. Review DNS server settings regularly to ensure they are correctly configured.
Stale DNS Records: Stale DNS records will cause DNS resolution issues and users can’t access websites and applications. Clean up stale DNS records regularly to keep your DNS zone clean and efficient.
Insecure DNS Protocols: Insecure DNS protocols like UDP can be a security risk and allow attackers to eavesdrop and tamper with DNS traffic. Use secure protocols like TCP or SSL/TLS to protect DNS traffic from eavesdropping and tampering.

How to Fix DNS Records Misconfigurations

For security researchers and teams hunting down vulnerabilities:

Audit Regularly: Review DNS settings periodically to ensure they are current and follow best practices.
Enable DNSSEC: Secure your DNS records with DNSSEC but make sure it’s implemented correctly to not introduce new vulnerabilities.
Restrict Zone Transfers: Configure zone transfers to only accept requests from authorized servers or IP addresses.
Close Open Resolvers: Limit who can query your DNS to block external abuse.
Monitor DNS Traffic: Use DNS monitoring tools to catch unusual activity, large query spikes or unauthorized access attempts.
Clean up Stale Records: Remove outdated or unused DNS records that no longer serve a purpose.
Set Proper TTL Values: Balance your TTL settings to reduce unnecessary queries while changes propagate quickly when needed.

DNS Server Security

DNS servers are part of the internet infrastructure and as such they need to be secured to prevent attacks and be reliable. Here are some DNS server security measures:

DNSSEC: Implement DNSSEC (Domain Name System Security Extensions) to add an extra layer of security and prevent DNS spoofing. DNSSEC signs DNS records digitally.
Secure DNS Protocols: Use secure DNS protocols like TCP or SSL/TLS to prevent eavesdropping and tampering. Secure protocols will protect DNS traffic from being intercepted and manipulated by malicious actors.
Rate Limiting: Implement rate limiting to prevent DNS amplification attacks and reduce the risk of DNS-based DDoS attacks. Rate limiting controls the number of DNS queries that can be processed within a time frame to mitigate malicious traffic.
Monitor DNS Traffic: Monitor DNS traffic to detect and respond to security threats. Use DNS monitoring tools to catch unusual activity, large query spikes, or unauthorized access attempts and take action to mitigate risks.
Monitor DNS Server Misconfigurations: use a website misconfiguration scanner like our own ProtocolGuard DNS Inspector to stay ahead of dangerous DNS misconfigurations.

Final thoughts

For security teams and researchers, DNS misconfigurations should never be ignored. One misstep can compromise your network, disrupt services, and create opportunities for attackers. By hunting for these vulnerabilities and following best practices you can secure your infrastructure and make DNS a strength, not a weakness.

Take the time to assess your DNS setup—because every secure network starts with a solid foundation.