The Hidden Costs of DNS Blocking Illegal Content

Governments use DNS blocking to fight piracy and CSAM. But shared IPs and CDNs mean innocent websites get caught in the crossfire.

Government institutions in every country have the right to police the internet to protect their citizens, businesses, and other institutions. Child safety, piracy, and exploitation are only some of the reasons why governments have to step in. The proliferation of this type of content is not only illegal, but it also jeopardizes businesses and children.

However, the government’s method of controlling the internet might be placing regular users in jeopardy. Carl Gahnberg, Senior Director, Policy Development and Research, noted on his blog at the Internet Society the problem:

“Growing concerns about online copyright infringement and child safety have led governments to regulate online services, which sometimes leads to content blocking or even making entire websites and apps unavailable.”

Blocking Illegal Websites with DNS

Blocking websites is more than just reporting them to ISPs to prevent user access. Governments are now preventing user access through DNS blocking. Using DNS blocking to prevent website access is a relatively effective method. But its unintended consequences go beyond preventing illegal content online.

DNS, according to Cloudflare, “is the phonebook of the Internet. Humans access information online through domain names, like nytimes.com or espn.com. Web browsers interact through Internet Protocol (IP) addresses. DNS translates domain names to IP addresses so browsers can load Internet resources.”

DNS blocking means the IP address is blocked even if there’s a request for the website address. It’s a really simple process because it will not even try to access the website through an IP address - it just blocks it from communicating. Because it’s a simple process, it’s relatively cost-effective and faster to deploy.

Take note that DNS blocking is not the same as website blocking. Website blocking is often targeted at specific URLs that require firewalls to prevent URLs from loading. Compared to DNS blocking, website blocking is costlier and will require more processing power.

Unintended Consequences of DNS Blocking

DNS blocking is a simple and effective method against illegal online content, but it comes at a cost to regular internet users. Websites often share infrastructure with other websites to ensure their online service or content is stable and reliable. Without shared content, a website could be rendered useless even if it is legally operating.

Content Delivery Networks or CDNs are also affected by DNS blocking. These services often give multiple websites the same IPv4 address due to scarcity. If one IPv4 address is blocked, other websites associated with the same IP address are also inaccessible.

One of the most popular examples of unintended consequences is Cloudflare's stance against the Italian government’s order to block their 1.1.1.1 DNS service due to content piracy. According to Ars Technica, Cloudflare is appealing the order and “had previously resisted a blocking order it received in February 2025, arguing that it would require installing a filter on DNS requests that would raise latency and negatively affect DNS resolution for sites that aren’t subject to the dispute over piracy.”

Blocking the Sources Instead of DNS

It is laudable that government institutions are looking for ways to prevent illegal and disturbing content online. However, DNS blocking may do more harm than good when they are not properly implemented. Blocking the culprits behind illegal content is more efficient because it ultimately blocks them from producing anything at all. By simply blocking access, the content is still live - it just is not available in select areas. Going after the creators of this content will ensure the material is not available to everyone.