DNS Filtering: How It Works & Why Your Business Needs It 

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Have you ever clicked a link and worried if it exposed your network to hackers?  

This happens more often than you’d think. Cyber threats are getting more advanced, and just one wrong click can lead to security problems like data breaches and malware. Here’s the thing: many businesses don’t realize they’re at risk until it’s too late. 

Even with firewalls and antivirus software, without DNS filtering, harmful websites and content can still get through. 

It might sound technical, but here we’ll explain how DNS filtering works and why it’s a critical protection layer today. 

What is DNS filtering and how does it work? 

To understand DNS filtering, you first need to know about DNS (Domain Name System). Think of DNS as the internet’s phone book. It translates easy-to-remember website names (like www.example.com)  to numerical IP addresses that computers use to connect to each other. Every time you enter a web address, a DNS query happens behind the scenes to take you to the right site. Without DNS, navigating the internet would be much harder. 

Now, DNS filtering steps in as an extra layer of protection. DNS filtering is a cybersecurity technique that blocks access to harmful websites at the DNS level. DNS filtering stops threats like malware and phishing sites before they cause problems. Think of it as an early warning system that keeps dangerous sites from doing any harm. 

Here’s a simple breakdown of how DNS filtering adds security to the DNS lookup process: 

  1. User website request. A user types a website URL into their browser, triggering a DNS lookup. 
  2. DNS query interception. The DNS filtering system catches the DNS query before it can reach the standard DNS server.  
  3. Content classification. The filter analyzes the content category of the requested website, such as whether it’s a news portal, a social media site, involves adult content, or is known for malicious activities. 
  4. Policy comparison. The filter then matches the website’s category against the organization’s set policies or a blocklist to determine if it aligns with allowed internet usage. 
  5. Response to user. If the site is safe, the DNS filter resolves the domain name to the correct IP address. This allows the user to access the website. But if the domain is on the blocklist, the DNS filter reroutes to an IP address that displays a “site blocked” message or directs the user to a custom block page. 

          2 Common types of DNS filtering 

          DNS filtering blocks harmful or unwanted content from your network. There are several methods to do this. Each method filters in a distinct way based on its view of threats. Here are the most common types: 

          1. Blocklist-based filtering  

          This is one of the most common methods. It blocks access to known malicious domains that security experts have identified as dangerous, using a list called a blocklist (a list of known harmful domains or IP addresses). This list includes websites associated with threats like malware, phishing, or ransomware.  

          How does it work? Cybersecurity experts maintain blocklists and constantly update them with new threats. Every time a website is requested, the DNS filtering system checks it against the blocklist. If the list includes the site, they deny access. This method blocks known threats but may miss new ones. 

          2. Allowlist-based filtering  

          This method works the opposite way; instead of blocking known harmful sites, it only allows access to specific, pre-approved domains. All other websites are blocked by default. 

          This approach is ideal for environments that need strict security control, like schools or corporate networks. For example, a company may use this to ensure employees can only access work-related websites. 

          Why use DNS filtering? 

          DNS filtering provides several important benefits for businesses, schools, and other organizations. Here’s why it’s so valuable: 

          Cybersecurity protection  

          The main reason to use DNS filtering is to guard against cyber threats. By blocking access to dangerous websites, DNS filtering helps protect against: 

          • Phishing attacks. These deceptive sites try to steal personal info like login details or credit card numbers. DNS filtering stops users from accessing known phishing sites. 
          • Malware and ransomware. It prevents users from downloading harmful software that can damage systems, steal data, or demand ransom to unlock files. 

          Beyond security, DNS filtering can block inappropriate or illegal content, like adult sites, gambling, or piracy. This keeps your network safe and compliant with ethical standards. 

          Boosts productivity  

          DNS filtering boosts productivity by blocking non-work-related sites during work hours. By blocking social media, gaming, and streaming platforms, it minimizes distractions and helps employees maintain their focus. This tool is crucial across all industries because it helps maintain high efficiency and maximize work output. 

          Helps with compliance  

          For some industries, DNS filtering is essential for meeting regulatory requirements. For example: 

          • Schools must block harmful content to follow U.S. laws like Children’s Internet Protection Act (CIPA). This creates a safer online environment for students. 
          • Healthcare organizations manage sensitive data that is often targeted by cyberattacks. They require robust security measures, and DNS filtering helps protect this data while also ensuring compliance with stringent regulations like Health Insurance Portability and Accountability Act (HIPAA). 

          DNS filtering vs. Web filtering: What’s the difference? 

          Many people confuse DNS filtering with web filtering, but each offers distinct advantages. DNS filtering blocks malicious websites by intercepting DNS queries before the sites load, while web filtering checks website content and blocks some types, like inappropriate or illegal material in real-time. 

          DNS filtering is faster because it operates at the DNS level, whereas web filtering provides more detailed control by evaluating web content in real-time. 

          For companies that focus on speed, DNS filtering is often the best solution. It works best with a specialized web server for added security. But businesses that need to block content may prefer web filtering. It is a more tailored option for blocking keywords or specific web content. 

          DNS filtering for businesses 

          As businesses expand and adopt remote and hybrid work models, network security becomes more challenging. DNS filtering is a scalable solution that protects both in-office and remote employees while simplifying network management. Here’s why DNS filtering is essential today: 

          Scalability for remote work 

          With more remote workers, businesses need scalable security. DNS filtering keeps devices safe at home, in cafés, or while traveling. It applies uniform security rules across devices. Furthermore, this removes the need for a constant VPN that makes it perfect for hybrid work. 

          Managing distributed networks 

          Large organizations with multiple offices or remote teams can benefit from managed DNS filtering solutions. These solutions allow consistent security policies across all locations and devices. Moreover, this simplifies management and ensures compliance with local regulations. 

          Reflecting on the role of DNS filtering 

          DNS filtering plays a key role in keeping your network secure by blocking harmful websites and preventing unauthorized content access. For businesses, it offers a scalable solution to protect both in-office and remote workers. 

          As cyber threats grow more advanced, pairing DNS filtering with additional security solutions can provide a robust defense, making it a simple yet powerful tool to keep your business safe. By incorporating DNS filtering into your cybersecurity strategy, you’re taking a proactive step to protect your network. This approach helps you keep up with the ever-changing internet, ensuring your defenses are always ready for the latest threats. 

          Frequently asked questions 

          How does DNS filtering block prohibited content? 

          DNS filtering blocks prohibited content by intercepting DNS requests and checking the requested domain names against a predefined list of undesirable or harmful websites. If a domain is found on this list, the filtering system blocks the request, preventing access to the content before it can even load in the user’s browser. This ensures that users are protected from accessing potentially dangerous or inappropriate material. 

          Can DNS filtering be bypassed? 

          Yes, if users switch DNS servers or use VPNs, but stricter DNS settings can reduce this risk. 

          What’s the difference between DNS filtering and web filtering? 

          DNS filtering blocks access to specific websites and filters domain names at the DNS level. This prevents users from visiting harmful or unwanted sites. Web filtering, on the other hand, checks web content directly and filters based on keywords, categories, or security threats. DNS filtering is faster and easier to implement. But web filtering gives more control over content. 

          How secure are DNS filtering solutions? 

          They are effective but should be used with other defenses like firewalls and antivirus for full protection. 

          Should I enable DNS filtering on my network? 

          Yes, it improves security and controls internet access, especially for remote users. 

          Does DNS filtering slow down internet speed? 

          No, it typically doesn’t affect speed and can sometimes improve it by blocking resource-heavy sites. 


          Serge John Mahinay
          Serge John Mahinay

          Serge is a Content Writer at Domain.com. With his background in SEO Content Writing, he incorporates his technical knowledge and deconstructs complex ideas and concepts into easy to digest texts. Outside work, he enjoys watching anime, playing video games, and learning about the newest AI trends.

          Serge John Mahinay
          Serge John Mahinay

          Serge is a Content Writer at Domain.com. With his background in SEO Content Writing, he incorporates his technical knowledge and deconstructs complex ideas and concepts into easy to digest texts. Outside work, he enjoys watching anime, playing video games, and learning about the newest AI trends.