When you type a web address (like www.example.com) into your browser, a Domain Name System (DNS) lookup occurs behind the scenes. This process translates the website’s domain name into its corresponding IP address (e.g., 123.45.67.89). Some people compare DNS to a phonebook or directory for the internet.
HOSTS.TXT to store hostnames. Updating and maintaining this single file quickly became cumbersome.Because DNS is so foundational to how the internet works, it’s also a key component in network security. Enter DNS filtering—a technology that applies policies to domains in real time, blocking malicious or unwanted websites before they even load.
DNS filtering is like a caller ID system for the Internet that can also block spam or malicious calls. It uses threat intelligence and categorization databases to identify whether a requested domain is safe or risky.
In short: DNS filtering checks the website’s category or reputation before the user connects, blocking anything that violates the policies you set—such as social media during work hours or known malicious domains.
First Line of Defense: DNS filtering intercepts threats at the domain level, which is often the earliest point a user interacts with an attack site.
Scalability: Because DNS filtering works at the DNS layer, it can be deployed across global or remote workforces with minimal hardware.
AI-Powered Categorization: Modern DNS filters (like DNSFilter) use machine learning to catch brand-new malicious domains in real time, rather than relying solely on static threat lists.
When a user attempts to access a domain (e.g., socialmedia123.com), a DNS query is sent to a DNS resolver. Here’s a basic overview if you’re using a DNS filtering solution:
All of this happens within a split second—the best DNS filtering solutions shouldn’t even be noticed by the end user unless they run into a blocked request.
If your organization blocks social media sites during work hours, you might see a company-branded block page stating, “Access Restricted,” whenever you try to visit Facebook between 9 a.m. and 5 p.m.
Beyond restricting unproductive or unsavory content, DNS filtering is crucial for cybersecurity. It prevents access to malicious sites used for phishing, ransomware, or cryptojacking attacks. Here’s why it matters:
In 2024, DNS-based DDoS attacks have seen a significant increase and have become a prominent attack vector. Cloudflare's Q1 2024 DDoS threat report highlighted a staggering 80% year-over-year (YoY) increase in DNS-based DDoS attacks, reaching around 54% of all network-layer attacks.
A 2021 IDC survey found that a staggering 87% of organizations experienced DNS attacks, indicating their widespread nature.
The Verizon Data Breach Investigations Report (DBIR) highlights that phishing remains a top attack vector, accounting for 36% of data breaches.
The average cost of a DNS attack was estimated at around $950,000 globally, with North American organizations facing even higher costs, averaging about $1 million per attack.
Information-stealing malware activity was encountered by 48% of organizations, highlighting the significant role DNS attacks play in spreading malware.
With around 200,000 new domains created every day, it’s easy for attackers to set up malicious URLs faster than you can block them manually. A DNS filtering solution with AI-driven scanning can identify and block harmful domains before a user even knows they exist.
Without DNS filtering, the burden falls on employees to spot suspicious websites on their own—an impossible task given the sheer volume of threats. DNS filtering automates this “spot check,” reducing human error and improving overall security posture.
Implementing DNS filtering is straightforward, especially as cloud-based solutions have matured. Here’s a quick guide on how to use DNS filtering effectively:
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Choose a Trusted DNS Filtering Provider Look for features like real-time AI detection, robust reporting, and easy policy management. Make sure the provider has global DNS servers for low-latency lookups. |
Configure Your Network Point your network’s DNS settings (router, firewall, or endpoint devices) to the filtering provider’s DNS servers. For remote users, consider a roaming client or VPN integration so DNS requests route through your filter even offsite. |
Define Policies and Categories Block malicious domains by default. Decide which content categories (social media, gambling, adult sites, etc.) to restrict. Create different policies for different user groups (e.g., employees, guests, children in education environments). |
Monitor and Report Review block logs to see attempted visits to malicious or unauthorized content. Use analytics to spot trends, fine-tune policy exceptions, and demonstrate ROI on security tools. |
Educate Users Let employees know why certain categories are blocked. Provide training on how to handle suspicious links, even when DNS filtering is in place. |
DNS filtering remains one of the most effective and low-overhead security measures available, seamlessly blending with other tools to block threats at the very first checkpoint. By thinking of DNS filtering as a form of preventive care, organizations can stop breaches before they happen and reduce overall security risks.
To get started—or to refine your existing setup—start your free trial of DNSFilter now.
Originally written by Serena Raymond in 2021. Updated for 2025 by the DNSFilter team to reflect the latest threat landscape, new statistics, and best practices.