It is no longer “trending”, but at the dawn of the millennium, the increasing globalization together with the rise of modern technology and especially the Internet gave birth to the term “Follow the Sun”. For the young or old and forgetful, here is what it was all about. For example, while online services that usually require continuous operation and worldwide accessibility at any given time, a service may stop working or become inaccessible to some users. Anytime. How to provide technical support for such service without forcing employees to be awake at night in a certain time zone? Spread the workers around the world so that you always have someone who has daytime (the Sun over their head) and can provide support for the online service. And if the worker can’t solve the issue, they would pass it to the next one in the direction of the moving sun, who would finish the job. The fact that the time needed to solve the request was not measured in hours, but in the number of revolutions of the request around the Earth, is not so important.
In this post, we describe the differences between the two widespread protocols for DNS encryption: DNS-over-TLS (DoT) and DNS-over-HTTPS (DoH). We compare the technical aspects of those protocols as well as their implications on user privacy. We also introduce Knot Resolver’s new built-in DoH support and explain some of our design decisions behind DoH.
The Internet is flooded with news about a new attack against DNS protocol called Side channel AttackeD DNS, or in short SAD DNS. The attack is described in detail in Cloudflare’s blog and I strongly recommend you to read it to grasp how it works and why it is novel.
Recently, version 3.0 of Knot DNS – an open-source implementation of an authoritative DNS server – has been released. Despite the version number, the software isn’t changing much. There are slightly more new features than in common feature releases such as 2.9. However, the features added in 3.0 don’t change any behaviour, unless the user turns them on. The migration from 2.9 to 3.0 is therefore seamless.
CZ.NIC Laboratories released the first public version of DNS Probe. It is a high-performance DNS traffic capture tool developed as a part of the ADAM project. Its essential function is to listen on a network interface, capture DNS traffic (both UDP and TCP), pair DNS queries with corresponding responses, and export consolidated records about every single DNS transaction observed on the wire. DNS Probe can be deployed either on the same machine as the DNS server, or on a separate monitoring computer that receives an exact copy of the DNS server’s traffic (e.g. via switch port mirroring).
DNS resolvers are constantly adding features while not removing any, but this trend cannot continue indefinitely because the software would eventually break under its own weight. Which features are used in practice and which can be safely removed? We present preliminary results of a survey among DNS resolver administrators, and also invite readers to participate in cross-vendor survey which is open until 2020-06-30.
As a planned milestone in the ADAM project (Advanced DNS Analytics and Measurements), CZ.NIC Laboratories in cooperation with CSIRT.CZ are about to commence regular operation of DNS crawler. This tool will periodically scan all second-level domains under TLD .cz, collect selected publicly available data about them, and process them further in various ways. Despite the name, the DNS crawler will collect data not only from DNS; it will also communicate with each domain’s web and e-mail server. We plan to run the tool with two periods: most data items will be collected on a weekly basis, only the contents of main web pages <domain>.cz or www.<domain>.cz will be retrieved less frequently – once a month. In addition, newly registered domains will be subject to an extra scrutiny: their data will be retrieved daily for the first two weeks of their existence. The DNS crawler software is designed so as to minimize the impact on the operation of second-level domains and network infrastructure in general. Data obtained from the crawler will be used for these principal purposes:
This article describes NXNSAttack, a newly discovered DNS protocol vulnerability which affects most recursive DNS resolvers. It allows to execute random subdomain attack using DNS delegation mechanism, resulting in big packet amplification factor.
As we have reported several times, after massive upgrades of the anycast DNS for the .CZ domain zone in recent years and building of the 100GbE DNS infrastructure, we are now focusing more on targeted tuning of the anycast operation. For example, we try launching new DNS stacks in the locations of significant DNS traffic sources, both abroad and in Czechia. The launch of the DNS stack on the CESNET network at the beginning of April is the most recent fruit of this work.
Recently, two entities have asked us to help them host their DNS zones and in both cases, we were happy to oblige. One of them was the Czech neutral peering node NIX.CZ, with which we often share technical know-how and help each other when it makes sense. The other one was the domain register of Guatemala operating the .gt ccTLD, which we humored as part of our long-term support of developing registers, like we have done the case with the registers of Angola, Malawi, Tanzania or North Macedonia.