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DNS scavenging is the process of removing stale DNS records, usually used together with DNS aging in order to free up space and improve system performance.

This feature also serves as a defensive measure by routinely clearing outdated records, lowering the risk of DNS-related vulnerabilities like cache poisoning, and ensuring a more secure network environment.

In this article, we will explore how DNS scavenging works, how to enable it, and why it plays such an important role in maintaining DNS security.

Read on to find out:

  • How DNS scavenging & aging works
  • Why remove stale DNS records
  • What are the benefits of DNS scavenging?
  • How to enable DNS Scavenging
  • Potential drawbacks
  • How to improve your DNS security

How does DNS scavenging work?

The Domain Name System (DNS) is a critical part of the internet infrastructure, providing a way to map human-readable domain names to numerical IP addresses. But because it was not built with security in mind, cyber criminals discovered various ways to exploit it.

DNS scavenging works by identifying and removing stale or outdated DNS records from a server. Here’s why you might need it:

  • When a DNS server receives a request for a domain name that it does not have in its records, it will send a query out to the internet root servers in an attempt to resolve the name.
  • If the root servers are unable to resolve the name, the DNS server will then check for any cached records of recently resolved names that may contain the requested name.
  • If the requested name is not found in either the root servers or in the DNS server’s cache, then the DNS server will return an error message to the requesting client.

DNS scavenging helps reduce these errors by periodically checking for and removing any stale records from both the root servers and from DNS caches. This helps ensure that users receive accurate information when they request it, and helps keep the internet running smoothly.

DNS scavenging and DNS aging

As I mentioned above, DNS scavenging and DNS aging are usually used together to identify old DNS records.

DNS aging identifies the ‘stale DNS record’ from the DNS server by keeping track of its ‘age’, and to be more precise – its time stamps. The age of the DNS record is the difference between the last time stamp and the current time of the server.

DNS scavenging uses this value to check if the record needs to be removed and, after identifying the eligible stale resource records, proceeds in removing them from the DNS server.

Why remove stale DNS records?

Stale DNS records can lead to problems within the DNS resolution (usually because they generate duplicate records), wasteful use of storage space, and reduced DNS server performance.

What are the benefits of DNS scavenging?

Helps prevent DNS cache poisoning

One of the biggest benefits of DNS scavenging is that it can help prevent DNS cache poisoning attacks.

DNS cache poisoning involves inserting false address records into a DNS cache, leading users to malicious sites.

By regularly removing stale or outdated records through DNS scavenging, the chances of old, possibly compromised records being used maliciously are reduced.

Makes servers less prone to overloading

Secondly, it can help protect against distributed denial of service (DDoS) attacks. In a DDoS attack, cybercriminals attempt to overload a server with requests in order to cause it to crash.

By scavenging DNS records, organizations can reduce the number of requests that their servers need to handle, making them less likely to be overloaded and more able to withstand an attack.

Keeps the internet running smoothly

Finally, DNS scavenging can help improve internet speed. This is because when records are removed from the DNS system, it reduces the amount of data that needs to be transferred between servers. This can lead to a reduction in latency and an improvement in overall internet speed.

Enabling DNS scavenging

DNS scavenging can be performed manually or set automatically. Manual scavenging involves manually checking for and removing old DNS records. Automatic scavenging uses software to automatically find and remove old DNS records.

DNS scavenging can be enabled on a per-server or per-zone basis. The difference between zone scavenging and server scavenging is that zone scavenging only affects a single zone, while server scavenging affects an entire server.

To learn more about what how this feature works on a Windows Server and how to enable it, follow the steps in this article from Microsoft Community.

Potential drawbacks of DNS scavenging

DNS scavenging can cause problems if it removes records that are still in use. This can happen if a device is turned off for a period of time, or if there is a network issue that prevents the device from contacting the DNS server.

When the device is turned back on or the network issue is resolved, the device will try to contact the DNS server to update its record, but will find that the record has been removed. This can cause errors and disruptions for users trying to access services on the affected device.

To avoid these problems, it’s important to ensure that devices are configured to update their DNS records regularly. This ensures that records are not removed prematurely, and that devices can quickly recover from any temporary network issues.

How can Heimdal® help?

While DNS scavenging and aging helps you maintain a clean DNS cache, it should be used in conjunction with other security measures, as part of a comprehensive DNS strategy.

If you want to take your DNS protection to the next level, you can count on Heimdal.

Our DNS security solution integrates a unique feature, called Predictive DNS, which scans user traffic on the go using artificial intelligence and machine learning. This solution helps you predict and stop DNS threats with precision, so you can secure both your endpoints and your network.

Whether on-site or remotely, Heimdal® DNS security scans your users’ traffic in real-time, blocking infected domains and preventing communication with cybercriminal infrastructures. This gives administrators complete confidence while securing internet browsing for all users.

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Wrapping up

DNS scavenging is an excellent practice for DNS maintenance, so it’s definitely worth giving it a try. DNS aging and scavenging maintain a cleaner and more secure DNS cache, less susceptible to poisoning attacks, as well as a smoother browsing experience.

If you want to improve your cybersecurity posture, you can always rely on Heimdal to assist you. Book a demo with us today and experience it firsthand.

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Author Profile

Madalina Popovici

Digital PR Specialist

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Madalina, a seasoned digital content creator at Heimdal®, blends her passion for cybersecurity with an 8-year background in PR & CSR consultancy. Skilled in making complex cyber topics accessible, she bridges the gap between cyber experts and the wider audience with finesse.

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