What is DNS Filtering?

DNS filtering is the process of using the Domain Name System to block user access to different websites and to filter out harmful or inappropriate content. If a site or category of sites has been deemed a threat, then its IP address is matched with the predefined name of the URL in the DNS filter and access is denied to the specific URL.

DNS filtering is essential for all organizations as it can limit the number of threats a network is exposed to, helping to significantly reduce the remediation workload for an organization’s IT teams.

How Does DNS Filtering Work?

Perimeter 81 DNS filtering service is based on a Domain Name System, or DNS and matches the domain name to its IP addresses. By typing a URL into your Perimeter 81 DNS Filtering dashboard, you’re instructing the DNS Resolver not to identify, retrieve, and display the website associated with its IP address in internet browsers. As a result, Perimeter 81 displays an alert to the user that the URL or content they were trying to access is blocked. Perimeter 81 DNS filtering service is compatible with Windows, Mac, Android, IPhone, Linux and iOS.

DNS filtering provides three different types of restrictive groups that allow IT teams to decide which IP sites and content will be blocked on their employee’s devices.


is the list of known harmful domains or IP addresses. When the DNS Resolver receives a URL query, and the name matches any of those inserted into the Blacklisted URLs field in Perimeter 81 (or uploaded as part of a list), then access is denied to the URL that user is requesting.


Web filtering also acts in the other direction as a whitelisting tool, giving IT administrators more control over the list of web destinations that employees are allowed to access. This two-pronged strategy is vital for herding users away from the bad and towards the good.

Category-Based Filtering

It’s easy to block access to the most popular and often compromised websites by category. Social media, pornography, news sites, gambling and gaming sites, and other categories can be removed in their entirety, and then supplemented with individual additions to either the Blacklisted URLs or Whitelisted URLs fields.

Perimeter 81’s DNS Filtering Advantages

Enhances network security by blocking access to malicious infected websites

Uses policy-based controls to oversee access with blocking and filtering

Prevents users from accessing material that could hinder productivity or cause offense

Additional security layer against malware coming from malicious or hacked sites

Discover How Perimeter 81 Can Help Your Organization

With Perimeter 81, we are providing secure, private and unrestricted internet access to businesses. To do so, we are transforming traditional network security technology with one unified Zero Trust Secure Network as a Service.

  • Complete visibility
  • Increased security
  • Precise segmentation
  • A highly scalable solution
  • A user-centric experience
  • Simple transition to cloud environments

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