What is DNS-over-HTTPS?

Josh Lamb
October 16, 2019

DNS-over-HTTPS is a DNS encryption method that works over HTTPS, it is also an alternative to the encryption method DNS-over-TLS.

New technology always bring unknown factors. Over the past year, leading web browsers began implementing a new internet protocol called DNS-over-HTTPS (DoH). DoH is a method for performing Domain Name System (DNS) resolution, using the HTTPS Protocol.

This represents a significant change in how browser vendors envision the future of DNS. Traditionally, DNS lookups have always taken place by the Operating System of the device. By using HTTPS, browser vendors are shifting this responsibility onto themselves.

1. How Does DNS Operate Today?

In order to understand why DoH came about, it’s necessary to understand how DNS currently operates. Since the inception of DNS 35 years ago, DNS queries have been performed in clear-text (unencrypted). Any unencrypted communication is vulnerable to exploitation. When it comes to DNS, these exploitations most commonly come in the form of tracking or spoofing.

Tracking is when your data is collected so that a profile is built of your browsing habits. This data can then be sold to advertisers or other parties. (without your knowledge!)

Spoofing is when DNS requests are forged. Mozilla presents an example where a user is connected to the WiFi at a retail store. The store’s DNS server could manipulate your DNS queries so that attempts to do a price comparison on a competitor’s website will fail or redirect.

The natural question to ask is “Who is the biggest perpetrator?” In many cases, the responsible party is the owner of the DNS server the user has connected to by default. Most people are not aware that when they connect to a new network, a DNS provider is automatically assigned to them. If you are at home or at work, this is usually your Internet Provider. If you are traveling to a coffee shop or airport, then by default you’ll use the DNS provider they give you (unless of course you're using a Roaming Client solution like the one DNSFilter provides). Free WiFi providers are often the largest culprits of DNS tracking.

2. What are Web Browsers Doing?

In response to the problems of tracking and spoofing, browser vendors are pushing forward the adoption of DoH. Early in September 2019, Mozilla announced plans to make DoH available by default for Firefox users in the United States. Shortly afterwards, Google announced similar plans for its upcoming build of Chrome. These decisions have introduced controversy and the implications are commonly misunderstood.

However, Mozilla and Google are going through an experimentation phase before fully switching over to DoH. They appear to both have a willingness to work with major DNS security providers (such as DNSFilter). Mozilla is the closest to full implementation, and has already worked directly with DNSFilter to ensure that Firefox is in full compliance with our service.

3. What does this mean for DNSFilter users?

The existence of DoH highlights the importance of maintaining control over your DNS data. By employing protective DNS like DNSFilter to secure your DNS, you are preventing DNS tracking and spoofing. Here are a few takeaways as we move into a DoH world:

  1. Using DNSFilter ensures the safety of your DNS information. Instead of relying on your internet provider or any individual network, you are sending your traffic to a company that won’t sell or manipulate your DNS data. This is not true of many “free DNS” providers.
  2. You have complete visibility. By using our Query Log tool, you are able to see exactly which DNS requests are being made on your network and to restrict users from accessing threats & inappropriate content.
  3. You can prevent DoH from interfering with your access policies. DNSFilter is 100% compatible with Firefox’s DoH and there is no action needed.

How Can I Secure My DNS?

The biggest question raised by DNS-over-HTTPS is how it will affect companies which have their own DNS security, such as DNSFilter. There are two steps you can take to ensure that DoH does not interfere with your filtering policies:

  1. You can prevent your browser from circumventing your policies by restricting DNS resolution to only DNSFilter. This is best done at the firewall level by blocking DoH addresses. This ensures that your DNS filtering policies will always remain in effect. For complete directions, checkout our help article on preventing circumvention. DNSFilter helps to maintain a community list of DoH servers so that system administrators can restrict access.
  2. You can setup DNS-over-TLS as a full-featured alternative. DNSFilter fully supports DNS-over-TLS using our Roaming Clients or DNS Relay. DNS-over-TLS is more comprehensive than DoH, because it encrypts all DNS traffic on your machine (rather than only web browser traffic). For this reason, it is DNSFilter’s preferred security method.

For more information on DNS encryption, check out our on-demand webinar that pits DoH against DoT.

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