How to block DoH with BlueCat’s threat feed option

Last updated on May 12, 2022.

DNS over HTTPS (DoH) is a method of encrypting DNS queries that has gained a lot of traction recently. In February 2020, DoH was added as a default setting in the Firefox browser.

Now ordinary users are jumping on the bandwagon. When the pandemic left everyone working from home, BlueCat noticed a 1,500% increase in DoH domain queries across its customer base. That dramatic surge in DoH usage continues to this day.

Opinions vary on the benefits of DoH, but one thing’s for sure: It reduces the visibility of network and security administrators to zero. If you’re charged with protecting a corporate network, you’re probably going to want to prevent users from accessing DoH services across the enterprise.

If you’re using a centralized DNS management platform like BlueCat, it’s easy to block DoH by adding known DoH resolvers to a response policy zone (RPZ). The longer-term challenge is adding any new DoH services that appear in the future to that block list.

BlueCat has made it easy by creating a new threat feed specifically for known DoH resolvers. BlueCat has long used threat feeds to bolster defense-in-depth. To disable DoH across the enterprise, all you have to do is enable this threat feed for DoH in either DNS Edge or DNS Integrity, and you’ll be all set. 

How to deploy the DoH threat feed in DNS Integrity

1. Log into BlueCat Address Manager.
2. Select the DNS tab. Tabs remember the page you last worked on, so select the tab again to ensure you’re on the configuration information page.
3. Under DNS Views, click a DNS View and then the Response Policy Zones sub-tab.
4. Under Response Policy Zones, click New and select Response Policy Zone.
5. Under General, add the name of the response policy zone.
6. Under Type, select the “BlueCat Threat Protection DoH Public Servers” option and apply other deployment parameters as desired.
7. Click update.

How to deploy the DoH threat feed in DNS Edge

1. Log into the DNS Edge user interface.
2. In the top navigation bar, select Policies.
3. Select an existing policy that uses the BlueCat Threat Protection domain list, and click Edit.
4. Select the BlueCat Threat Protection DoH Public Servers option.
5. Click save and apply.

BlueCat is keeping an eye out for any new DoH resolvers and adding them to the threat feed. As a result, you’re covered even as DoH usage evolves.

Our care portal contains more information about DoH threat feed options, including detailed technical notes. You can also learn more about the pros and cons of DoH in a webinar with BlueCat’s Chief Strategy Officer Andrew Wertkin.