Security Magazine logo
search
cart
facebook twitter linkedin youtube
  • Sign In
  • Create Account
  • Sign Out
  • My Account
Security Magazine logo
  • NEWS
    • Security Newswire
    • Technologies & Solutions
  • MANAGEMENT
    • Leadership Management
    • Enterprise Services
    • Security Education & Training
    • Logical Security
    • Security & Business Resilience
    • Profiles in Excellence
  • PHYSICAL
    • Access Management
    • Fire & Life Safety
    • Identity Management
    • Physical Security
    • Video Surveillance
    • Case Studies (Physical)
  • CYBER
    • Cybersecurity News
    • More
  • BLOG
  • COLUMNS
    • Cyber Tactics
    • Leadership & Management
    • Security Talk
    • Career Intelligence
    • Leader to Leader
    • Cybersecurity Education & Training
  • EXCLUSIVES
    • Annual Guarding Report
    • Most Influential People in Security
    • The Security Benchmark Report
    • The Security Leadership Issue
    • Top Guard and Security Officer Companies
    • Top Cybersecurity Leaders
    • Women in Security
  • SECTORS
    • Arenas / Stadiums / Leagues / Entertainment
    • Banking/Finance/Insurance
    • Construction, Real Estate, Property Management
    • Education: K-12
    • Education: University
    • Government: Federal, State and Local
    • Hospitality & Casinos
    • Hospitals & Medical Centers
    • Infrastructure:Electric,Gas & Water
    • Ports: Sea, Land, & Air
    • Retail/Restaurants/Convenience
    • Transportation/Logistics/Supply Chain/Distribution/ Warehousing
  • EVENTS
    • Industry Events
    • Webinars
    • Solutions by Sector
    • Security 500 Conference
  • MEDIA
    • Videos
      • Cybersecurity & Geopolitical Discussion
      • Ask Me Anything (AMA) Series
    • Podcasts
    • Polls
    • Photo Galleries
  • MORE
    • Call for Entries
    • Classifieds & Job Listings
    • Continuing Education
    • Newsletter
    • Sponsor Insights
    • Store
    • White Papers
  • EMAG
    • eMagazine
    • This Month's Content
    • Advertise
  • SIGN UP!
CybersecurityManagementSecurity Enterprise ServicesSecurity Leadership and ManagementLogical SecuritySecurity & Business ResilienceSecurity Education & TrainingCybersecurity News

Disappearing DNS: DoT and DoH, Where one Letter Makes a Great Difference

By Darren Anstee
Encryption Future - Security Magazine
February 6, 2020

The somewhat ironic acronym DoH (domain name system (DNS) over HTTPS) demonstrates that the authors of the standard have a good sense of humor. However, as DoH has been implemented by major Internet companies it has become a key topic in many discussion forums, where the expression “DOH!” can be heard as an expression of concern, disappointment and misunderstanding at the impact DoH can have.

Let’s start by taking a step back and look at the original goals of DoH and DoT (DNS over Transport Layer Security (TLS)). There seems to be a consensus for advocates of private Internet use that encryption is a good thing, and that encryption of DNS is needed to prevent network operators from gaining visibility into the sites and services their users lookup (and then visit). Two protocols have been created to achieve this encryption: DoT and DoH. While both offer encryption of DNS data using the same TLS protocol, there are some very important differences:

  • Protocol layering: while DoT is essentially DNS over TLS, DoH is in fact DNS over HTTP over TLS.
  • Different port numbers: DoT traffic uses a dedicated port 853, and can thus be distinguished at the network layer. DoH uses port 443 (HTTPS) due to the protocol layering.
  • Different capabilities: DoT is largely the same DNS as we know it, while DoH to an extent combines features of DNS and HTTP. The most notable, extended DoH capabilities are the options to “push” DNS data from the server rather than “pull” it, and ability for web browsers to define what DNS resolver will be used rather than the underlying computer operating system (and the administrators of that system).

Having two options to achieve a similar goal has caused some divergence within the Internet community as some organizations started deploying and promoting DoT, and others picked up DoH. The first group largely consists of service providers and enterprises. For them DoT is an evolution as it does not fundamentally change the way networks are designed, operated and secured. However, web companies and browser developers placed their bet on DoH, offering users the ability to bypass DNS services offered by service providers and configured by system administrators. They are offering their own cloud DNS services, with their differentiator being a combination of better privacy and increased performance – two things that sound attractive for an end-user.

From the network operator perspective though, if users migrate to DoH the visibility operators have into the over-the-top services their customers utilize will diminish, and their ability to defend/protect their users from the threats out on the Internet will also be reduced. There are downsides.

At NETSCOUT, we decided to look at adoption of both protocols by monitoring aggregated DoH and DoT traffic in a few large networks. Over one month, looking at statistics such as total number of requests and responses, sources of requests (Internet users) and sources of responses (DoT or DoH servers) we found that on average there are seven times more DoT requests than DoH. The vast majority of requests over both protocols were served by Google and Cloudflare. Other notable DoT services that we have observed were offered by AdGuard and Clean Browsing. When it comes to DoH, Quad9 and SecureDNS were also among the leaders.

It is challenging to categorize users of both protocols as they vary a lot: we have observed residential and business subscribers, data centers and educational networks of varying sizes. What caught our attention is that one of the most active DoH sources in one specific network was a Tor egress node. A combination of DoH and Tor allows a user to not only hide the DNS information itself, but also anonymizes the source of DNS requests, which results in another additional layer of complexity for applications looking to monitor DNS data and network usage.

Obviously, time will tell if DoT continues to prevail or whether DoH will start to gain ground. As mentioned at the beginning of the article there is a hot debate going on right now about the direction the Internet industry should take. Suffice to say that even nation state authorities are involved in the debate, which speaks to the level and importance of the discussion. For NETSCOUT, researchers and others out there across the Internet, these are interesting times as we will be able to see how Internet architecture adapts to a fundamental shift in DNS, a key element of the control plane.

If DoH becomes prevalent and web companies become the main DNS providers, we will see another round of centralization. (We say “another” because content centralization and the dominance of CDNs occurred throughout the past decade. In this brave new world, HTTPS would become de-facto a universal transport protocol, which would make ideas like OSI and TCP/IP layered models less relevant.)

As both protocols get more traction, network operators of all types are becoming more and more concerned about the impact a lack of DNS visibility will have on their day to day activities. Just imagine that a DoH service fails for some reason – either internal outage or a DDoS attack - for a typical non-technical mobile or broadband user this would likely present itself as “No Internet connection.” This would likely lead to a support call to the service provider and ‘blame’ targeting that service provider - who actually has nothing to do with the DoH service causing the problem. These kinds of issues are a major concern across the industry. There are interesting times ahead.

 

This article originally ran in Today’s Cybersecurity Leader, a monthly cybersecurity-focused eNewsletter for security end users, brought to you by Security Magazine. Subscribe here.

KEYWORDS: data center security domain name systems (DNS) attacks encryption internet security privacy regulation

Share This Story

Looking for a reprint of this article?
From high-res PDFs to custom plaques, order your copy today!

Darren anstee

Darren Anstee is Chief Technology Officer, SBO International, NETSCOUT. Anstee has 20 years of experience in pre-sales, consultancy and support for telecom and security solutions. As Chief Technology Officer, SBO International, at NETSCOUT, Darren works across the research, strategy, and pre-sales aspects of Arbor's traffic monitoring, threat detection and mitigation solutions for service providers and enterprises around the world. He is an integral part of Arbor's Security Engineering & Response Team (ASERT).

Recommended Content

JOIN TODAY
To unlock your recommendations.

Already have an account? Sign In

  • Security's Top Cybersecurity Leaders 2024

    Security's Top Cybersecurity Leaders 2024

    Security magazine's Top Cybersecurity Leaders 2024 award...
    Security Enterprise Services
    By: Security Staff
  • cyber brain

    The intersection of cybersecurity and artificial intelligence

    Artificial intelligence (AI) is a valuable cybersecurity...
    Columns
    By: Pam Nigro
  • artificial intelligence AI graphic

    Assessing the pros and cons of AI for cybersecurity

    Artificial intelligence (AI) has significant implications...
    Technologies & Solutions
    By: Charles Denyer
Subscribe For Free!
  • Security eNewsletter & Other eNews Alerts
  • eMagazine Subscriptions
  • Manage My Preferences
  • Online Registration
  • Mobile App
  • Subscription Customer Service

More Videos

Sponsored Content

Sponsored Content is a special paid section where industry companies provide high quality, objective, non-commercial content around topics of interest to the Security audience. All Sponsored Content is supplied by the advertising company and any opinions expressed in this article are those of the author and not necessarily reflect the views of Security or its parent company, BNP Media. Interested in participating in our Sponsored Content section? Contact your local rep!

close
  • Crisis Response Team
    Sponsored byEverbridge

    Automate or Fall Behind – Crisis Response at the Speed of Risk

  • Perimeter security
    Sponsored byAMAROK

    Why Property Security is the New Competitive Advantage

  • Duty of Care
    Sponsored byAMAROK

    Integrating Technology and Physical Security to Advance Duty of Care

Popular Stories

Pills spilled

More than 20,000 sensitive medical records exposed

Coding on screen

Research reveals mass scanning and exploitation campaigns

Laptop in darkness

Verizon 2025 Data Breach Investigations Report shows rise in cyberattacks

Computer with binary code hovering nearby

Cyberattacks Targeting US Increased by 136%

White post office truck

Department of Labor Sues USPS Over Texas Whistleblower Termination

2025 Security Benchmark banner

Events

May 22, 2025

Proactive Crisis Communication

Crisis doesn't wait for the right time - it strikes when least expected. Is your team prepared to communicate clearly and effectively when it matters most?

September 29, 2025

Global Security Exchange (GSX)

 

View All Submit An Event

Products

Security Culture: A How-to Guide for Improving Security Culture and Dealing with People Risk in Your Organisation

Security Culture: A How-to Guide for Improving Security Culture and Dealing with People Risk in Your Organisation

See More Products

Related Articles

  • internet of things

    The Rise of the Internet of Things

    See More
  • Looking for Clues

    Suite success: Three steps executive teams should take to prevent and survive a data breach

    See More
  • cyber6-900px.jpg

    Making the business case for security by design

    See More
×

Sign-up to receive top management & result-driven techniques in the industry.

Join over 20,000+ industry leaders who receive our premium content.

SIGN UP TODAY!
  • RESOURCES
    • Advertise
    • Contact Us
    • Store
    • Want More
  • SIGN UP TODAY
    • Create Account
    • eMagazine
    • eNewsletter
    • Customer Service
    • Manage Preferences
  • SERVICES
    • Marketing Services
    • Reprints
    • Market Research
    • List Rental
    • Survey/Respondent Access
  • STAY CONNECTED
    • LinkedIn
    • Facebook
    • YouTube
    • X (Twitter)
  • PRIVACY
    • PRIVACY POLICY
    • TERMS & CONDITIONS
    • DO NOT SELL MY PERSONAL INFORMATION
    • PRIVACY REQUEST
    • ACCESSIBILITY

Copyright ©2025. All Rights Reserved BNP Media.

Design, CMS, Hosting & Web Development :: ePublishing