The Domain Name System (DNS) is critical for internet functionality, but when DNS hygiene is neglected, organizations leave themselves open to risk.
Poor DNS hygiene isn’t just a technical oversight, it’s a strategic imperative that impacts everything from brand reputation and email deliverability to overall security posture and operational resilience.
Maintaining optimal DNS hygiene is akin to practicing good dental or home maintenance: consistent, proactive attention prevents significant problems down the line. As your digital ecosystem grows more complex, the importance of a well-managed DNS infrastructure escalates, making DNS hygiene a foundational element of a robust cybersecurity strategy.
What is a domain health check?
A domain health check is a comprehensive audit and assessment of your domain’s DNS records and associated configurations. It’s a process designed to identify potential issues, vulnerabilities, and inefficiencies within your DNS infrastructure. Think of it as a diagnostic for your domain, similar to a physical examination for a patient, aiming to detect any underlying problems before they manifest into critical health issues for your online presence. This check involves scrutinizing various aspects of your DNS setup, from the records themselves to their management and security, ensuring that everything is functioning optimally and securely.
Why check domain security?
Monitoring your domain’s health and security helps your organization to be proactive about your domain hygiene and serves several key functions.
Protects your domain’s reputation
A healthy DNS is intrinsically linked to a strong domain reputation. When your DNS records are accurate, consistently configured, and secure, it signals to the internet that your domain is a trustworthy entity. Conversely, misconfigurations, stale records, or signs of compromise can lead search engines, email providers, and other online services to view your domain with suspicion. This can negatively impact search engine rankings, lead to emails being flagged as spam, and ultimately erode the credibility you’ve worked hard to build. Proactive DNS hygiene ensures that your domain consistently resolves correctly, reinforcing its legitimacy and trustworthiness across the digital ecosystem.
Ensures email deliverability
Email remains a vital communication channel for businesses, and its effectiveness hinges directly on DNS configuration. Protocols like Sender Policy Framework (SPF), DomainKeys Identified Mail (DKIM), and Domain-based Message Authentication, Reporting & Conformance (DMARC) rely heavily on accurate DNS records to authenticate outgoing emails. If these records are misconfigured, outdated, or absent, email servers may reject your messages or route them to spam folders. Maintaining proper DNS hygiene, particularly by correctly implementing and updating SPF, DKIM, and DMARC records, ensures your emails reach their intended recipients, preserving your communication channels and avoiding lost business opportunities.
Improves email open rates
Beyond simply landing in the inbox, the accuracy and security of your DNS records directly influence how recipients perceive your emails. When emails are consistently authenticated through robust DNS-based mechanisms like SPF, DKIM, and DMARC, they are more likely to be trusted by email clients. This trust translates into higher engagement, including increased open rates. When users see legitimate, authenticated emails from your domain, they are more inclined to open and interact with them. However, poorly managed DNS can cause emails to be marked as spam, drastically reducing open rates and diminishing the impact of your email marketing and communication efforts.
Meets email authentication standards
Adhering to email authentication is necessary for effective email communication. DNS plays a foundational role in implementing these standards. SPF records authorize specific mail servers to send email on behalf of your domain. DKIM digitally signs emails, providing a cryptographic way to verify that the message hasn’t been tampered with in transit. DMARC builds upon SPF and DKIM, specifying how receiving mail servers should handle emails that fail authentication checks and providing valuable reporting. Neglecting the DNS configurations for these protocols directly hinders your ability to meet these essential authentication requirements, jeopardizing email deliverability and sender reputation.
Avoid misconfigurations
DNS is a complex system with numerous record types and settings, making misconfigurations a common pitfall. An incorrectly configured A record can point a website to the wrong IP address, leading to downtime. A faulty MX record can prevent emails from being received. These errors can arise from human error, complex setup processes, or simply a lack of ongoing maintenance. A thorough domain health check meticulously reviews all DNS records, identifying and rectifying these misconfigurations before they impact service availability, user experience, or brand perception. Proactive identification and correction of these errors are hallmarks of good DNS hygiene.
Reduce attack surface
Every active DNS record, especially those associated with cloud services or subdomains, represents a potential entry point for attackers. If a subdomain is no longer actively used but its DNS record still points to a cloud resource that has been deprovisioned or is inadequately secured, it creates a “dangling DNS” vulnerability. Attackers can then claim this resource and exploit it, associating it with their malicious activities. Regularly auditing and cleaning up DNS records, ensuring that only necessary and actively managed records remain, significantly shrinks your attack surface, making it harder for malicious actors to find and exploit vulnerabilities.
Simplify maintenance
A cluttered and disorganized DNS zone file is a maintenance nightmare. It becomes difficult to track what each record is for, when it was last updated, and if it’s still necessary. This complexity increases the risk of errors during future changes and makes troubleshooting more challenging. Maintaining clean DNS records (removing duplicates, defunct entries, and unnecessary subdomains) simplifies the overall management of your DNS infrastructure. This streamlined approach reduces the time and effort required for routine tasks and upgrades, making your IT operations more efficient and less prone to errors.
Keep zones clean
DNS zone files act as the authoritative directory for a domain’s DNS records. Over time, as services are added, removed, or migrated, these zone files can accumulate obsolete, redundant, or conflicting entries. This “clutter” not only complicates management but also increases the risk of misconfigurations and security vulnerabilities. Keeping zones clean means actively auditing and removing any records that are no longer in use or have been superseded. Meticulous housekeeping ensures that your DNS zone file is an accurate and efficient reflection of your current digital assets, minimizing potential points of failure and security gaps.
What are dangling DNS records?
Dangling DNS records, often referred to as “subdomain takeover vulnerabilities,” occur when a DNS record points to a service or resource that is no longer provisioned or managed by the domain owner.
For instance, a subdomain might be configured to point to a cloud hosting provider’s service. If that service is later cancelled or deleted without the corresponding DNS record being removed, the DNS record becomes “dangling.”
An attacker can then provision a new instance of that cloud service and point it to the dangling DNS record, effectively taking control of that subdomain. This allows them to host malicious content, launch phishing campaigns, or intercept traffic intended for the legitimate domain, severely damaging brand reputation and user trust.
What are some common DNS attacks?
The security of DNS is paramount, as numerous attack vectors exploit its vulnerabilities. Understanding these threats is the first step in fortifying your DNS infrastructure.
- DNS Spoofing: Also called cache poisoning, DNS spoofing involves an attacker slipping false records into a DNS resolver’s cache. When users ask for a trusted site, they are quietly rerouted to a malicious one.
- DNS Amplification Attacks: In this type of DDoS attack, an attacker sends tiny spoofed DNS queries that trigger huge responses, all aimed at the victim.
- DNS Reflection Attacks: This type of attack is closely related to amplification attacks. The attacker forges the victim’s IP address so DNS servers “reflect” their replies at the target, overwhelming it with traffic.
- NXDOMAIN Attacks: An attacker floods a DNS server with requests for domains that don’t exist. This consumes server resources until real users feel the slowdown.
- DNS Tunneling: DNS is abused as a covert channel to exfiltrate data or sneak malware traffic past firewalls.
- Domain Hijacking: Attackers compromise a registrar or DNS management account and change DNS records outright. Legitimate traffic is sent wherever the attacker wants.
- Random Subdomain Attacks: A cousin of NXDOMAIN attacks. The attacker generates endless unique subdomains under a real domain, bypassing caches and hammering authoritative DNS servers.
- Phantom Domain Attacks: The attacker references domains whose name servers don’t respond. Resolvers keep retrying, consuming more and more resources.
How to check if your DNS is healthy
Ensuring DNS health is an ongoing process that requires regular checks and proactive management. It’s not a one-time fix but a continuous commitment to maintaining the integrity and security of your DNS infrastructure.
Review TTLs
Time-To-Live (TTL) values in DNS records determine how long a DNS resolver caches a particular record before querying the authoritative name server again. While essential for performance and reducing server load, improperly configured TTLs can prolong the impact of malicious changes or misconfigurations. For instance, a very high TTL on a compromised record could mean that a malicious change remains cached and active for an extended period. Conversely, excessively low TTLs can increase DNS query load. Reviewing and setting appropriate, often dynamic, TTLs is a crucial aspect of DNS hygiene, allowing for faster propagation of legitimate changes and quicker mitigation of malicious activities.
Remove unused records
Unused DNS records represent a significant security risk and clutter. These can include records for deprecated services, old subdomains that are no longer active, or placeholder entries. Each of these records, if not properly removed, can become a target for exploitation. For example, a dangling DNS record pointing to an abandoned cloud service can be hijacked by an attacker. Regularly auditing and removing all records that are no longer necessary or associated with active services is a core practice in DNS hygiene, effectively shrinking the attack surface and preventing potential subdomain takeovers.
Remove stale subdomains
Stale subdomains are essentially dangling DNS records for entire subdomains that are no longer in use but still exist in the DNS zone. This often happens when entire applications or services are decommissioned, but their DNS entries are left behind. These stale subdomains can be exploited by attackers to impersonate legitimate services. For instance, a company might decommission an old marketing microsite, but if its DNS records are not removed, an attacker could potentially claim the associated cloud infrastructure and use the subdomain for phishing. Proactive management ensures that all subdomains are actively associated with functioning, secured resources.
Identify redundant or conflicting records
Within a DNS zone file, redundancy and conflicts can arise, often due to oversight or during complex migration processes. Having multiple A records for the same hostname pointing to different IP addresses, or conflicting CNAME records, can lead to unpredictable behavior and service disruption. It also complicates troubleshooting. Identifying and resolving these redundant or conflicting records is a critical hygiene practice. It ensures that the DNS resolution process is deterministic and reliable, preventing unexpected downtime and improving the overall stability of your online services.
Monitor zone changes
The DNS zone file is a living document that should reflect the current state of your domain’s infrastructure. Unauthorized or undetected changes to this file can be a strong indicator of a security breach or a critical misconfiguration. Implementing a robust monitoring system for zone file changes is therefore essential. This involves tracking all modifications, noting who made them, when, and why. Real-time alerts for suspicious or unapproved changes enable rapid detection and response, allowing security teams to investigate and mitigate potential threats before they cause significant damage.
Improve your DNS hygiene with Digicert
The consequences of neglecting DNS hygiene can be severe, including everything from brand erosion and email deliverability failures to significant security breaches and costly downtime. Investing in robust DNS hygiene is not merely a technical precaution but a strategic business decision that safeguards reputation, revenue, and resilience.
To effectively manage DNS hygiene, organizations should develop clear policies, foster team education, and integrate DNS management into broader IT workflows. For those facing complexity or resource constraints, exploring managed DNS services can provide the necessary expertise. By treating DNS hygiene not as an afterthought but as a core component of their digital strategy, organizations can build a more secure, reliable, and trustworthy online presence, ensuring they are well-equipped to navigate the evolving threat landscape. Prioritizing the cleanliness and security of your DNS is investing in the foundational integrity of your digital identity.
Don’t let a lapse in DNS hygiene cause unnecessary downtime or performance issues for your enterprise. Trust DigiCert DNS to simplify and optimize your DNS management. Take advantage of our industry-leading features and ensure a seamless online experience for your users.
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