Filed Under: Windows

DNS Firewall – Everything You Need to Know About It


Written by Jack Lin

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DNS Firewall

With the increasing demands on security, networking, and IT teams, tools that do not cost much and reduce workloads are something that you look for.

DNS Firewall is one such piece of equipment. People who have no idea about what a DNS Firewall is and how it works continue to read this blog.

Introduction to DNS Firewall

In basic terms, DNS Firewalls work like traditional firewalls, where it redirects or blocks end-users from opening malicious sites.

When it comes to the difference, DNS Firewall can be applied to a different phase and layer; explicitly, data feeds like threat intelligence, which is applied to the DNS (Domain Name System).

It circumvents the visibility loss that makes the traditional firewalls a bit less effective because of the momentous increases in end-to-end encrypted traffic.

By the way, for people curious about the importance of a firewall, just read more.

Why Should Users Choose DNS Firewall?

DNS Firewall protects users against malware installation, data exfiltration, and identity theft.

Additionally, there are lots of other reasons for using this kind of Firewall as a unit of your security at multiple layers. Some important features of a DNS Firewall include the following:

Educate the End-users

If you attempt to link to a bad domain, then one can enlighten the end-user regarding the danger he has just avoided. For instance, potentially connecting to a phishing website.

It can either be carried out through a landing page that the end-user is redirected to or by contacting him directly. Thus, you turn a worse decision into a positive teaching occasion.

Free Up the Busy Team

By using this type of Firewall, you mitigate some serious problems automatically, which could arise on the network when it is being compromised. So, it provides the team with some free time for focusing on other pressing security and network issues.

Gain Insight to Be Practical

DNS Firewall offers more visibility to conceded clients or users on the network. It enables users to take some immediate actions with no time lags, which are either being warned by third parties or discovering the problem at a later date after the outbreak, which could be days, weeks, or months.

It is Simple to Apply and Easy to Maintain

After the application of this Firewall to the DNS, all clients on the network, such as IoT devices, get protected against accessing malicious websites. It also lessens deployment resources.

At the same time, the DNS Firewall continuously updates the data feeds against which latent connections are examined. Thus, it removes the requirement for updates and upgrades.

Brand Protection

For big brands, online security breaches could have a big impact on their business. To understand such consequences, you can look at the momentous data breach that happened with British Airways in the United Kingdom.

So, it is significant to have multi-layer security for keeping the users and company networks completely safe.

Low Cyber Risk Insurance Costs

Probably, insurance and other associated costs do not come under the budget and responsibilities of your department.

However, it is most likely that people in your company will be pleased to know that executing the DNS Firewall could reduce the cyber risk insurance amounts significantly and effectively.

How to Implement DNS Firewall?

Generally, there are three methods for implementing DNS Firewall. It is great to point out that all of these methods employ ‘threat intelligence data feeds’ for identifying bad domains. However, these methods differ in how users can utilize or access the feeds.

On-premises Open Source Software

Here, threat intelligence data feeds are moved through IXFR/AXFR to the DNS resolver in the form of zone files. Initially, DNS Firewall was designed to be a translatable and open standard, whereas its former home was BIND.

Now, various other DNS servers like Unbound, Knot, and PowerDNS offer support for employing DNS Firewall threat feeds.

On-premises Appliance

An internal application or solution that is located within the network works as a management system for the security infrastructure of your DNS.

It makes use of threat intelligence data feeds. As per the supplier, users enjoy the flexibility to select the preferred data feed supplier.


A service provider has its own DNS resolver secured by the DNS Firewall featuring threat intelligence data feeds and accessed by customers like managed services.

How Does DNS Firewall Work?

Now, it is time to know how this Firewall actually works. So, let’s have a look below!

DNS Firewall

Normal DNS Resolvers

When the end-users attempt to visit a domain or website, the DNS resolver queries a root server. After this, a high-level domain server and then the site’s server complete the resolution of the end-users request. The request of the client for accessing the website takes place irrespective of whether the website is nasty or not.

DNS Resolvers with DNS Firewall

Throughout the resolution zone process that comprises threat intelligence, data sets are queried. The entreated domain is examined for potential risks of security against these data sets. If some match is found, then the request gets redirected or blocked.

Phishing site with no DNS Firewall
Phishing site with DNS Firewall NXDOMAIN enabled
Phishing Landing Page Example

When the DNS Firewall is enabled, the end-users who have attempted to access a phishing site that, has been prevented from accessing and consequently secured from the potential danger that it could lead to.

Furthermore, as the mitigation occurs at the DNS level, there’s no need for the user to install other programs or software on the workstation. Now, it is time you should consider other things while implementing DNS Firewall.

Key Features of DNS Firewall

A DNS firewall typically offers several essential features to ensure comprehensive protection. Some of the key features include:

  1. Real-time Threat Detection: DNS firewalls continuously monitor DNS traffic and detect potential threats in real time, allowing prompt action to be taken.
  2. DNS Query Filtering: The firewall filters DNS queries based on various criteria, such as domain reputation, IP reputation, and behavior analysis.
  3. Blacklisting and Whitelisting: Administrators can create custom blacklists and whitelists to control access to specific domains or block known malicious domains.
  4. Behavioral Analysis: DNS firewalls employ advanced algorithms to analyze DNS traffic patterns and detect anomalies that may indicate malicious activity.
  5. Logging and Reporting: Comprehensive logging and reporting capabilities enable administrators to analyze DNS traffic, identify security incidents, and fine-tune firewall rules.

How Much Does DNS Firewall Cost?

Price is the key factor when thinking of buying new hardware or services. Consider if users have a capital budget or if they are looking for a solution that can fit into their operational budget, depending on the subscription.

On-Premises Appliance

Here, prices are lower as compared to the cloud service. This is because users uninstall something onto their network.

But look if you need to pay any additional charges for using ancillary services on the appliances.

On-Premises Open Source Software

The price remains the lowest within this category as users transfer threat intelligence feeds into their own DNS resolvers. Thus, they would not have to pay any hardware costs.

Cloud Service

When it comes to price, cloud service is the most expensive one per user. This is so because of the infrastructure costs of the provider, which is in addition to the price of distributing the threat intelligence within their network.

However, the setup of the cloud service is comparatively easy. Here, users lose control and flexibility because it is a service that you need to share with various users. Therefore, you even end up reimbursing for the data feeds that you actually do not require.

Challenges and Limitations of DNS Firewalls

While DNS firewalls are an effective security tool, they do have certain challenges and limitations. Some of these include:

  1. Encryption and DNS-over-HTTPS (DoH): As more traffic is encrypted, itbecomes challenging for DNS firewalls to inspect the contents of encrypted DNS traffic, such as DNS-over-HTTPS (DoH) requests. This can limit the effectiveness of the firewall in detecting and blocking malicious activities.
  2. False Positives and False Negatives: DNS firewalls may occasionally generate false positives, blocking legitimate DNS queries, or false negatives, allowing potentially malicious traffic to pass through undetected. Regular monitoring and fine-tuning of firewall rules can help minimize these occurrences.
  3. Sophisticated Attacks: Advanced and sophisticated attacks, such as DNS tunneling and DNS exfiltration, may evade detection by traditional DNS firewalls. Organizations need to continuously update their firewall rules and stay informed about emerging threats to mitigate these risks.

The field of DNS firewall technology is continually evolving to keep up with the ever-changing cybersecurity landscape. Some future trends to watch out for include:

  1. Machine Learning and AI: DNS firewalls are likely to leverage machine learning and artificial intelligence techniques to enhance threat detection capabilities and improve the accuracy of identifying malicious activities.
  2. Advanced Behavioral Analysis: DNS firewalls will incorporate more advanced behavioral analysis algorithms to detect subtle patterns and anomalies in DNS traffic, allowing for more effective threat prevention.
  3. Integration with Cloud Services: As organizations increasingly move their infrastructure and services to the cloud, DNS firewalls will integrate seamlessly with cloud-based security solutions to provide consistent protection across on-premises and cloud environments.
  4. Enhanced DoH Support: With the rise of encrypted DNS traffic, DNS firewalls will adapt to better handle DNS-over-HTTPS (DoH) requests, ensuring comprehensive protection without compromising privacy.


In today’s digital landscape, where cyber threats are on the rise, implementing robust security measures is essential. A DNS firewall serves as a crucial component in safeguarding networks and preventing malicious activities.

By effectively monitoring and filtering DNS traffic, organizations and individuals can significantly enhance their network security, protect sensitive data, and mitigate the risks associated with various DNS-based attacks.


Q1. Can I use a DNS firewall for personal use?

Yes, DNS firewalls are not limited to large organizations. Individuals and small businesses can also benefit from using a DNS firewall to enhance their network security.

Q2. Does a DNS firewall affect internet speed?

When properly configured and maintained, a DNS firewall should not significantly impact internet speed. In some cases, it can even improve performance by blocking connections to slow or unreliable servers.

Q3. Can a DNS firewall replace traditional firewalls?

While DNS firewalls provide specialized protection against DNS-specific threats, they should not be seen as a replacement for traditional firewalls. Both types of firewalls complement each other to provide a comprehensive security infrastructure.

Q4. How often should I update my DNS firewall rules?

Regularly updating your DNS firewall rules is essential to ensure protection against the latest threats. Stay informed about emerging threats and update your firewall rules accordingly.

Q5. Are DNS firewalls effective against sophisticated attacks?

While DNS firewalls are effective against many types of attacks, sophisticated attacks such as DNS tunneling and exfiltration may require additional security measures. Continuous monitoring and staying up to date with evolving threats are crucial in mitigating these risks.


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