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DoH—toward more privacy


The Domain Name System (DNS) serves as the address book for the internet. Because they built DNS with scalability and consistency in mind, the developers did not consider how it could be exploited, manipulated, misused, or even harnessed for good.

However, we can no longer overlook the need for DNS protection as an integral component of the internet. Bad actors often target DNS, so most IT professionals increasingly see the protection of DNS layers as a necessary security element. In terms of making networks more resilient to cyberattacks, DNS is the perfect control point because all Internet resource lookups, both network and user-based, are routed via external DNS servers. Unfortunately, organizations are often content to let their ISP handle the DNS requests. Thus, they have no insight into which requests are being made and responded to.

DNS over HTTPS (DoH)

Since its inception in 1983, the DNS has scaled to hold over 335 million domains, acting as gateways to billions of URLs. A far-sighted and brilliant solution, the DNS was built around performance and scalability. As a result, by merely looking at organizations' or individuals' DNS requests, you can easily determine how people use the internet, where and when they browse websites, access applications, and even what devices and tools they use on your network. Because each of these requests is not encrypted (and the DNS resolver isn’t verified), clear text DNS reveals this information and exposes the integrity of the responses to compromise. Privacy and security were not a consideration. DoH seeks to address that.

DoH: Improving privacy and security

DoH specifically addresses the fundamental privacy and security limitations of DNS. Much like how a browser connects to a secure website through HTTPS, DoH allows DNS requests to be secured. The system first verifies the resolving server through a certificate, and then it establishes an SSL connection. All DNS requests are then communicated over this connection, encrypted, and protected courtesy of HTTPS. Thus, DoH improves privacy because encrypted DoH requests are not easily monitored or intercepted. DoH also adds the assurance that only the DNS provider of choice is aware of these DNS requests. Likewise, DoH improves security by encrypting DNS requests. Not only does this verify that the DoH DNS resolver specified is the one providing resolution, but it also ensures that the requests themselves are protected and have not been altered or compromised.

DoH: How encryption causes security problems

Because DoH can manage DNS requests for applications directly, it has the potential to circumvent the configured DNS resolver provided on your network. This ability can cause new security and technical problems for organizations. For example, if a device makes DNS requests for a domain that hosts known botnet or malware sites, it would be essential to have visibility into these actions and make corresponding security decisions. But, when these DNS requests are managed directly by an application through DoH, network logs no longer provide visibility into whether those DNS requests are occurring. Unmanaged DoH, in effect, blindsides existing security controls.

Furthermore, DoH can circumvent most commercial DNS filtering solutions. When an application makes a DNS request directly through DoH and not through the OS’s DNS resolver, you cannot apply filtering. Not only is the system exposed to the threat, but the system won’t log the actual event. This lost ability to filter and report on DNS requests considerably weakens overall network security.

Conclusion

DoH is an important new protection for DNS requests. It improves the overall privacy and security of the DNS requests that every organization makes when using the internet. But it’s also essential that organizations adopt this technology without losing the significant security benefits they get by managing and controlling DNS request traffic today. Be sure to consider all the angles.

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Mustapha Benmbarek

Mustapha works with startups and companies of any size to support their innovation. In his role as Solutions Architect at Rackspace, he leverages his experience to help people bring their ideas to life, providing guidance and technical assistance on cloud based and AWS architectures.

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