DNS filtering

A security service that blocks access to known malicious or unwanted websites by checking each domain lookup against threat lists before a connection is made.

Every time a device visits a website, it first asks a DNS server for that site's address. DNS filtering services intercept these requests and refuse to resolve domains known to host malware, phishing pages or other threats. Businesses can also block categories of content that are inappropriate for the workplace.

DNS filtering is an efficient, low-cost layer of protection. It can stop a user from reaching a phishing page even after they click a bad link, and it can prevent some malware from contacting its control servers. Because it works at the domain lookup level, it can protect many types of devices, including those that cannot run traditional security software. The Canadian Internet Registration Authority (CIRA) offers a DNS firewall service aimed at Canadian organizations, and several other providers offer similar options.

Practical tip: make sure DNS filtering also protects laptops when staff work from home or travel, not only devices in the office. Agent-based or cloud-managed options can extend protection wherever the device goes.