What is DNS Filtering? 

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Every online interaction starts with a Domain Name System (DNS) query, making DNS a cost-effective spot for enforcing security policies and Acceptable Usage Policies (AUPs) through DNS filtering. Also known as Protective DNS or a DNS Firewall, Domain Name System filtering is a method to block access to specific websites or web addresses based on predefined criteria. It intercepts and analyzes DNS queries before they reach their destination, allowing organizations and individuals to control internet browsing by blocking malicious, inappropriate, or non-productive sites. 

In this article, we will explore the benefits of DNS filtering, explain how DNS filtering works, and offer considerations for implementing DNS filtering effectively. Learn how DNS filtering can enhance your cybersecurity and improve productivity by controlling internet access. 

What is DNS Filtering and How Does it Work? 

DNS, or Domain Name System, functions as the internet’s phonebook, translating human-friendly domain names like `www.example.com` into numerical IP addresses required for devices to communicate. When a user types a web address into a browser, the DNS process begins by sending a query to a DNS resolver, also known as a recursive server. The resolver is often managed by the Local Area Network (LAN) administrators, provided by a small office or home router-firewall, or from an Internet Service Provider as part of your network connection details. This resolver initiates a series of requests to navigate the DNS hierarchy and locate the authoritative DNS server that holds the resource records for the domain. Once the IP address is retrieved, it is returned to the user’s browser, which then establishes a connection to the server hosting the website. This entire process occurs in milliseconds, enabling seamless navigation across the internet. 

DNS filtering is one of the capabilities built into DNS recursive servers that allow administrators to block domains, subdomains, Fully-Qualified Domain Names (FQDNs), hostnames, and IP addresses. DNS filtering helps to stop computers on their network from accessing malicious websites or other services. It is a very cost-effective way to protect network assets and is often an organization’s first line of defense against online threats. 

DNS Filtering can help to mitigate a large variety of attacks and policy violations: 

  • Phishing websites are designed to capture login credentials or other personally identifiable information (PII). 
  • Links to malware distribution tools and installation software. 
  • Servers for malware command and control. 
  • Websites that feature content in violation of policy, such as pornography, gambling, or dating. 

How does DNS filtering work? 

A DNS filter is a powerful tool that helps protect your network by using a DNS resolver to maintain lists such as allowlists, watchlists, or blocklists. These lists contain categorized domain names to identify safe, suspicious, and malicious websites. When a DNS query is received, the filter analyzes the request and checks it against its lists to determine if the domain is safe or harmful. The filter then responds to the query based on its assessment. 

The way a filter operates depends on the categorization of the incoming domain and the specific rules set for the filter. These filter rules can vary based on the DNS filter and web application security model in use. However, all filters follow a similar process. Understanding how filters work is crucial for enhancing cybersecurity and ensuring effective web filtering. The three types of lists in a DNS filter decide on queries as follows: 

  • Safe domains on the allowlist are permitted 
  • Questionable domains on the watchlist might be flagged for review  
  • Malicious domains on the blocklist are blocked 

When a domain is blocked, the DNS filter responds to the query with the IP address of a sinkhole or block page. This page not only notifies the user that the website was blocked for their safety but also serves a dual purpose. It records connection details, which are then forwarded to the Security Operations Center (SOC) for review. This enables the SOC to analyze attempted access to malicious or policy-violating sites, enhancing an organization’s overall security posture by identifying potential threats in their network environment. 

Protective DNS is an advanced DNS filtering technology. Next-generation Protective DNS includes the following features:  

  • Real-time threat intelligence updates: Protective DNS continuously updates its databases in real-time so that it can quickly identify and block new threats as they emerge. 
  • AI-based threat detection: This uses machine learning to identify and block new and emerging threats in real-time. 
  • Dynamic categorization: This feature continuously monitors websites, categorizing them based on their content. It ensures that the filter always has up-to-date information for making decisions. 
  • Granular policies: With this feature, organizations can have different DNS filtering rules and policies for separate groups or devices within their network. This allows for more targeted protection against specific risks. 
  • More choices of blocklists: DNS filters can pull from a larger database of malicious sites. 
  • Personalized additive protection: Organizations can customize their blocklists with additional security policies that cater specifically to their needs. For example, organizations may want to block access to social media websites during work hours. 
  • Intelligent rules-based filtering: This feature allows for more control over how a filter handles specific types of domains or requests based on user activity and device type. 
  • Endpoint client: This extends your DNS filtering to devices on networks that you do not control, such as hotel or coffeeshop Wi-Fi. 
  • Selective proxy: Instead of blocking sites outright, traffic bound for them is sent to a web filtering proxy for further analysis. 

Examples of DNS Filtering 

DNS filtering serves multiple purposes. Here are some examples: 

  • Enterprise Security: Enhance corporate network security by blocking access to phishing sites and other malicious domains, protecting sensitive company data. 
  • Parental Controls: Provide families a means to manage children’s internet use by restricting access to inappropriate or harmful websites. 
  • Educational Institutions: Ensure a safe online environment for students by filtering content and preventing access to non-educational or distracting websites. 
  • Healthcare Data Protection: Protect patient information in healthcare systems by blocking potential cyber threats targeting sensitive medical data. 
  • Public Wi-Fi Protection: Secure public Wi-Fi networks in places like cafes and airports by preventing users from accessing risky sites and spreading malware. 
  • Compliance and Regulatory Adherence: Aid businesses in meeting regulatory requirements by restricting access to websites that could result in data breaches or non-compliance. 
  • Business Productivity: Increase workplace productivity by limiting access to non-work-related websites and reducing distractions during work hours.  

The benefits of DNS Filtering for business (Success) 

DNS filtering provides numerous benefits for both individuals and organizations. Here are some key advantages: 

  • Enhanced Security: DNS filtering blocks access to malicious websites, helping to prevent malware infections and data breaches. Improve your network security by using DNS filtering. 
  • Boosted Productivity: By restricting access to distracting websites like social media or gaming sites, DNS filtering enhances productivity in workplaces and educational environments. Increase workplace efficiency with DNS filtering. 
  • Customizable DNS Policies: Organizations can tailor DNS filtering policies to meet specific needs, offering a personalized approach to internet management. Customize DNS filtering to suit your organization’s requirements. 
  • Cost-Effective Solution: DNS filtering is a budget-friendly option for network security and content filtering, eliminating the need for additional hardware or software. Save costs with DNS filtering solutions. 
  • Easy Implementation: Implementing DNS filtering is quick and straightforward, with no disruptions to existing network infrastructure. Enjoy hassle-free DNS filtering deployment. 

How to configure and use DNS filtering 

While most organizations use some kind of DNS filtering, there are some basic tactics that you can use to get more value and capabilities from your DNS filtering, including the following: 

Import and Use DNS Filter Lists

Implementing DNS filter lists is a straightforward process that enhances your DNS filtering strategy. Filter lists provide predefined sets of web categories or specific domains that can be easily imported into your DNS filtering system. To begin, you can choose from a variety of filter lists available online that suit your organization’s policies. Once selected, import the lists into your DNS filtering platform. These lists can typically be imported via the platform’s dashboard, following which you will be able to apply them to devices or user groups. Regular updates and maintenance of these lists ensure that your filtering system is up to date with the latest threats and content categories, reinforcing your security and productivity measures effectively. 

Make and Enforce an Acceptable Use Policy

Creating an Acceptable Use Policy (AUP) is a critical step in managing how users access and use the internet within your organization. Begin by defining the policy’s purpose, setting expectations for responsible network use, and outlining what constitutes acceptable and unacceptable behavior. Once the policy is drafted, communicate it effectively to all users, ensuring that everyone understands the rules and the rationale behind them. Make the policy easily accessible by hosting it on your organization’s intranet or distributing it via email. Enforcing the policy involves using DNS filtering to automatically block access to non-compliant sites and activities outlined in the AUP. Regularly review and update the policy to adapt to changing internet usage patterns and potential security threats. This process ensures that your organization maintains a secure, productive, and respectful online environment. 

Use a Protective DNS Provider

Choosing a protective DNS provider is essential for strengthening your network’s security posture. These providers offer advanced security features that guard against malicious sites, phishing attacks, and other web-based threats. When selecting a protective DNS provider, consider factors such as their reputation in the industry, the scope of their threat intelligence, and the ease of integrating their services into your existing infrastructure. A reliable provider will not only block harmful content but will also offer analytics and reporting tools, enabling you to monitor web traffic effectively. By utilizing a protective DNS provider, you enhance the overall safety of your network, ensure compliance with organizational policies, and promote a secure and efficient web usage environment for all users. 

Implement Endpoint Clients for Remote Devices

To extend the benefits of your protective DNS across all devices, including those used remotely, it is crucial to implement endpoint clients. These clients ensure that even when devices are off network, they still adhere to your organization’s DNS filtering policies. Installation is typically straightforward, with most providers offering client software that can be deployed quickly across your device fleet. Once installed, the endpoint client routes DNS queries through your protective DNS server, maintaining consistent security measures regardless of location. Using endpoint clients not only protects remote devices from potential threats but also helps maintain compliance with company policies, providing peace of mind for both IT administrators and users. 

Block frequent attacks with DNS filtering 

DNS filtering is an essential tool for organizations and individuals looking to enhance their online security, productivity, and compliance. With its ability to block access to malicious websites and restrict users’ internet use, DNS filtering helps protect against cyber threats and ensure a safer browsing experience. Whether it is for enterprise security, parental controls, or regulatory adherence, DNS filtering offers numerous benefits that make it a valuable addition to any network.  

How Vercara can help

Vercara offers a next-generation protective DNS solution known as UltraDDR. This solution is designed to act proactively, stepping into action before an attack rather than after it occurs. UltraDDR counters adversaries effectively and blocks malicious queries, allowing businesses to stay ahead of threats and attacks. 

UltraDDR focuses on the discovery and mapping of adversary infrastructure. This powerful tool combines this with real-time communication pattern analysis, shifting security defenses from reactive to proactive. 

  1. AI-Backed Decision Engine: Identify malicious domains based on the infrastructure that they use and before they can be used in an attack. 
  2. Lists Engine: Block queries to malicious domains by bringing your own blocklists. 
  3. Global network: UltraDDR employs a global network of secure recursive servers allowing you to tap into security, reliability, and swift response times. 
  4. Content web filtering: Easily enforce company Internet usage policies with category-based content web filtering. This includes block or allow lists. 
  5. Adaptive policy engine: The UltraDDR engine uses years of historical domain data combined with real-time analysis of adversary communication patterns. This is crucial in identifying and preventing attacks before they even start. 

Vercara helps global industries secure their online presence and perform at scale with maximum reliability. We have helped secure the Olympic Games, and we can help you too. Contact us today to give your online assets greater security and performance capabilities. 

 

Published On: July 8, 2023
Last Updated: January 22, 2025

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