Understanding DNS Query Composition at B-Root

The Domain Name System (DNS) is part of critical internet infrastructure, as DNS is invoked whenever a remote server is accessed (an URL is visited, an API request is made, etc.) by any application. DNS queries are served in hierarchical manner, with most queries served locally from cached data, and a small fraction propagating to the top of the hierarchy - DNS root name servers. Our research aims to provide a comprehensive, longitudinal characterization of DNS queries received at B-Root over ten years. We sampled and analyzed a 28-billion-query large dataset from the ten annual Day in the Life of the Internet (DITL) experiments from 2013 through 2022. We sought to identify and quantify unexpected DNS queries, establish longitudinal trends, and compare our findings with published results of others. We found that unexpected query traffic increased from 39.57% in 2013 to 67.91% in 2022, with 36.55% of queries being priming queries. We also observed growth and decline of Chromium-initiated, random DNS queries. Finally, we analyzed the largest DNS query senders and established that most of their traffic consists of unexpected queries.Comment: 20 pages with 18 figures and 1 table. Published and presented at the 2022 IEEE/ACM International Conference on Big Data Computing, Applications and Technologies (BDCAT

Attacking and securing Network Time Protocol

Network Time Protocol (NTP) is used to synchronize time between computer systems communicating over unreliable, variable-latency, and untrusted network paths. Time is critical for many applications; in particular it is heavily utilized by cryptographic protocols. Despite its importance, the community still lacks visibility into the robustness of the NTP ecosystem itself, the integrity of the timing information transmitted by NTP, and the impact that any error in NTP might have upon the security of other protocols that rely on timing information. In this thesis, we seek to accomplish the following broad goals: 1. Demonstrate that the current design presents a security risk, by showing that network attackers can exploit NTP and then use it to attack other core Internet protocols that rely on time. 2. Improve NTP to make it more robust, and rigorously analyze the security of the improved protocol. 3. Establish formal and precise security requirements that should be satisfied by a network time-synchronization protocol, and prove that these are sufficient for the security of other protocols that rely on time. We take the following approach to achieve our goals incrementally. 1. We begin by (a) scrutinizing NTP's core protocol (RFC 5905) and (b) statically analyzing code of its reference implementation to identify vulnerabilities in protocol design, ambiguities in specifications, and flaws in reference implementations. We then leverage these observations to show several off- and on-path denial-of-service and time-shifting attacks on NTP clients. We then show cache-flushing and cache-sticking attacks on DNS(SEC) that leverage NTP. We quantify the attack surface using Internet measurements, and suggest simple countermeasures that can improve the security of NTP and DNS(SEC). 2. Next we move beyond identifying attacks and leverage ideas from Universal Composability (UC) security framework to develop a cryptographic model for attacks on NTP's datagram protocol. We use this model to prove the security of a new backwards-compatible protocol that correctly synchronizes time in the face of both off- and on-path network attackers. 3. Next, we propose general security notions for network time-synchronization protocols within the UC framework and formulate ideal functionalities that capture a number of prevalent forms of time measurement within existing systems. We show how they can be realized by real-world protocols (including but not limited to NTP), and how they can be used to assert security of time-reliant applications-specifically, cryptographic certificates with revocation and expiration times. Our security framework allows for a clear and modular treatment of the use of time in security-sensitive systems. Our work makes the core NTP protocol and its implementations more robust and secure, thus improving the security of applications and protocols that rely on time

Attacking the Network Time Protocol

We explore the risk that network attackers can exploit unauthenticated Network Time Protocol (NTP) traffic to alter the time on client systems. We first discuss how an on-path attacker, that hijacks traffic to an NTP server, can quickly shift time on the server\u27s clients. Then, we present a extremely low-rate (single packet) denial-of-service attack that an off-path attacker, located anywhere on the network, can use to disable NTP clock synchronization on a client. Next, we show how an off-path attacker can exploit IPv4 packet fragmentation to shift time on a client. We discuss the implications on these attacks on other core Internet protocols, quantify their attack surface using Internet measurements, and suggest a few simple countermeasures that can improve the security of NTP

Addressing the challenges of modern DNS:a comprehensive tutorial

The Domain Name System (DNS) plays a crucial role in connecting services and users on the Internet. Since its first specification, DNS has been extended in numerous documents to keep it fit for today’s challenges and demands. And these challenges are many. Revelations of snooping on DNS traffic led to changes to guarantee confidentiality of DNS queries. Attacks to forge DNS traffic led to changes to shore up the integrity of the DNS. Finally, denial-of-service attack on DNS operations have led to new DNS operations architectures. All of these developments make DNS a highly interesting, but also highly challenging research topic. This tutorial – aimed at graduate students and early-career researchers – provides a overview of the modern DNS, its ongoing development and its open challenges. This tutorial has four major contributions. We first provide a comprehensive overview of the DNS protocol. Then, we explain how DNS is deployed in practice. This lays the foundation for the third contribution: a review of the biggest challenges the modern DNS faces today and how they can be addressed. These challenges are (i) protecting the confidentiality and (ii) guaranteeing the integrity of the information provided in the DNS, (iii) ensuring the availability of the DNS infrastructure, and (iv) detecting and preventing attacks that make use of the DNS. Last, we discuss which challenges remain open, pointing the reader towards new research areas

The Impact of DNSSEC on the Internet Landscape

In this dissertation we investigate the security deficiencies of the Domain Name System (DNS) and assess the impact of the DNSSEC security extensions. DNS spoofing attacks divert an application to the wrong server, but are also used routinely for blocking access to websites. We provide evidence for systematic DNS spoofing in China and Iran with measurement-based analyses, which allow us to examine the DNS spoofing filters from vantage points outside of the affected networks. Third-parties in other countries can be affected inadvertently by spoofing-based domain filtering, which could be averted with DNSSEC. The security goals of DNSSEC are data integrity and authenticity. A point solution called NSEC3 adds a privacy assertion to DNSSEC, which is supposed to prevent disclosure of the domain namespace as a whole. We present GPU-based attacks on the NSEC3 privacy assertion, which allow efficient recovery of the namespace contents. We demonstrate with active measurements that DNSSEC has found wide adoption after initial hesitation. At server-side, there are more than five million domains signed with DNSSEC. A portion of them is insecure due to insufficient cryptographic key lengths or broken due to maintenance failures. At client-side, we have observed a worldwide increase of DNSSEC validation over the last three years, though not necessarily on the last mile. Deployment of DNSSEC validation on end hosts is impaired by intermediate caching components, which degrade the availability of DNSSEC. However, intermediate caches contribute to the performance and scalability of the Domain Name System, as we show with trace-driven simulations. We suggest that validating end hosts utilize intermediate caches by default but fall back to autonomous name resolution in case of DNSSEC failures.In dieser Dissertation werden die Sicherheitsdefizite des Domain Name Systems (DNS) untersucht und die Auswirkungen der DNSSEC-Sicherheitserweiterungen bewertet. DNS-Spoofing hat den Zweck eine Anwendung zum falschen Server umzuleiten, wird aber auch regelmäßig eingesetzt, um den Zugang zu Websites zu sperren. Durch messbasierte Analysen wird in dieser Arbeit die systematische Durchführung von DNS-Spoofing-Angriffen in China und im Iran belegt, wobei sich die Messpunkte außerhalb der von den Sperrfiltern betroffenen Netzwerke befinden. Es wird gezeigt, dass Dritte in anderen Ländern durch die Spoofing-basierten Sperrfilter unbeabsichtigt beeinträchtigt werden können, was mit DNSSEC verhindert werden kann. Die Sicherheitsziele von DNSSEC sind Datenintegrität und Authentizität. Die NSEC3-Erweiterung sichert zudem die Privatheit des Domainnamensraums, damit die Inhalte eines DNSSEC-Servers nicht in Gänze ausgelesen werden können. In dieser Arbeit werden GPU-basierte Angriffsmethoden auf die von NSEC3 zugesicherte Privatheit vorgestellt, die eine effiziente Wiederherstellung des Domainnamensraums ermöglichen. Ferner wird mit aktiven Messmethoden die Verbreitung von DNSSEC untersucht, die nach anfänglicher Zurückhaltung deutlich zugenommen hat. Auf der Serverseite gibt es mehr als fünf Millionen mit DNSSEC signierte Domainnamen. Ein Teil davon ist aufgrund von unzureichenden kryptographischen Schlüssellängen unsicher, ein weiterer Teil zudem aufgrund von Wartungsfehlern nicht mit DNSSEC erreichbar. Auf der Clientseite ist der Anteil der DNSSEC-Validierung in den letzten drei Jahren weltweit gestiegen. Allerdings ist hierbei offen, ob die Validierung nahe bei den Endgeräten stattfindet, um unvertraute Kommunikationspfade vollständig abzusichern. Der Einsatz von DNSSEC-Validierung auf Endgeräten wird durch zwischengeschaltete DNS-Cache-Komponenten erschwert, da hierdurch die Verfügbarkeit von DNSSEC beeinträchtigt wird. Allerdings tragen zwischengeschaltete Caches zur Performance und Skalierbarkeit des Domain Name Systems bei, wie in dieser Arbeit mit messbasierten Simulationen gezeigt wird. Daher sollten Endgeräte standardmäßig die vorhandene DNS-Infrastruktur nutzen, bei Validierungsfehlern jedoch selbständig die DNSSEC-Zielserver anfragen, um im Cache gespeicherte, fehlerhafte DNS-Antworten zu umgehen