Roland van Rijswijk-Deij

DNSSEC and its potential for DDoS attacks: a comprehensive measurement study

Over the past five years we have witnessed the introduction of DNSSEC, a security extension to the DNS that relies on digital signatures. DNSSEC strengthens DNS by preventing attacks such as cache poisoning. However, a common argument against the deployment of DNSSEC is its potential for abuse in Distributed Denial of Service (DDoS) attacks, in particular reflection and amplification attacks. DNS responses for a DNSSEC-signed domain are typically larger than those for an unsigned domain, thus, it may seem that DNSSEC could actually worsen the problem of DNS-based DDoS attacks. The potential for abuse in DNSSEC-signed domains has, however, never been assessed on a large scale. In this paper we establish ground truth around this open question. We perform a detailed measurement on a large dataset of DNSSEC-signed domains, covering 70% (2.5 million) of all signed domains in operation today, and compare the potential for amplification attacks to a representative sample of domains without DNSSEC. At first glance, the outcome of these measurements confirms that DNSSEC indeed worsens the DDoS phenomenon. Closer examination, however, gives a more nuanced picture. DNSSEC really only makes the situation worse for one particular query type (ANY), for which responses may be over 50 times larger than the original query (and in rare cases up to 179x). We also discuss a number of mitigation strategies that can have immediate impact for operators and suggest future research directions with regards to these mitigation strategies.

Booters — An analysis of DDoS-as-a-service attacks

In 2012, the Dutch National Research and Education Network, SURFnet, observed a multitude of Distributed Denial of Service (DDoS) attacks against educational institutions. These attacks were effective enough to cause the online exams of hundreds of students to be cancelled. Surprisingly, these attacks were purchased by students from Web sites, known as Booters. These sites provide DDoS attacks as a paid service (DDoS-as-a-Service) at costs starting from 1 USD. Since this problem was first identified by SURFnet, Booters have been used repeatedly to perform attacks on schools in SURFnets constituency. Very little is known, however, about the characteristics of Booters, and particularly how their attacks are structure. This is vital information needed to mitigate these attacks. In this paper we analyse the characteristics of 14 distinct Booters based on more than 250 GB of network data from real attacks. Our findings show that Booters pose a real threat that should not be underestimated, especially since our analysis suggests that they can easily increase their firepower based on their current infrastructure.

A High-Performance, Scalable Infrastructure for Large-Scale Active DNS Measurements

The domain name system (DNS) is a core component of the Internet. It performs the vital task of mapping human readable names into machine readable data (such as IP addresses, which hosts handle e-mail, and so on). The content of the DNS reveals a lot about the technical operations of a domain. Thus, studying the state of large parts of the DNS over time reveals valuable information about the evolution of the Internet. We collect a unique long-term data set with daily DNS measurements for all the domains under the main top-level domains (TLDs) on the Internet (including .com, .net, and .org, comprising 50% of the global DNS name space). This paper discusses the challenges of performing such a large-scale active measurement. These challenges include scaling the daily measurement to collect data for the largest TLD (.com, with 123M names) and ensuring that a measurement of this scale does not impose an unacceptable burden on the global DNS infrastructure. The paper discusses the design choices we have made to meet these challenges and documents the design of the measurement system we implemented based on these choices. Two case studies related to cloud e-mail services illustrate the value of measuring the DNS at this scale. The data this system collects is valuable to the network research community. Therefore, we end this paper by discussing how we make the data accessible to other researchers.

DNSSEC meets real world: dealing with unreachability caused by fragmentation

The Domain Name System (DNS) provides a critical service on the Internet: translating host names into IP addresses. Traditional DNS does not provide guarantees about authenticity and origin integrity. DNSSEC, an extension to DNS, improves this by using cryptographic signatures, at the expense of larger response messages. Some of these larger response messages experience fragmentation, and may, as a result of that, be blocked by firewalls. As a consequence, resolvers behind such firewalls will no longer receive complete responses from name servers, leading to certain Internet zones becoming unreachable because no translation into IP addresses can be performed. Our research shows that despite ongoing efforts to educate firewall and resolver administrators, as much as 10 percent of all resolvers suffer from fragmentation-related connectivity issues. Given that some major Internet companies were reluctant to adopt even a technology like IPv6 if it meant that a small percentage of their users would have connectivity issues, it is clear that we cannot rely on resolver/firewall operators alone to tackle this issue. The contribution of this article is that it a) quantifies the severity of these DNSSEC deployment problems, based on extensive measurements at a major National Research and Education Network (NREN) and backed up by validation of these findings at an independent second location, b) proposes two potential solutions at the DNS authoritative name server side, and c) validates both solutions, again based on extensive measurements on the operational network of this major NREN. The article concludes with a recommendation favoring our first solution. The first solution is relatively simple to implement and gives DNS zone operators control over this problem without having to rely on all resolver operators solving the issue

Measuring the Adoption of DDoS Protection Services

Distributed Denial-of-Service (DDoS) attacks have steadily gained in popularity over the last decade, their intensity ranging from mere nuisance to severe. The increased number of attacks, combined with the loss of revenue for the targets, has given rise to a market for DDoS Protection Service (DPS) providers, to whom victims can outsource the cleansing of their traffic by using traffic diversion. In this paper, we investigate the adoption of cloud-based DPSs worldwide. We focus on nine leading providers. Our outlook on adoption is made on the basis of active DNS measurements. We introduce a methodology that allows us, for a given domain name, to determine if traffic diversion to a DPS is in effect. It also allows us to distinguish various methods of traffic diversion and protection. For our analysis we use a long-term, large-scale data set that covers well over 50\% of all names in the global domain namespace, in daily snapshots, over a period of 1.5 years. Our results show that DPS adoption has grown by 1.24x in our measurement period, a prominent trend compared to the overall expansion of the namespace. Our study also reveals that adoption is often lead by big players such as large Web hosters, which activate or deactivate DDoS protection for millions of domain names at once.

Making the Case for Elliptic Curves in DNSSEC

The Domain Name System Security Extensions (DNSSEC) add authenticity and integrity to the DNS, improving its security. Unfortunately, DNSSEC is not without problems. DNSSEC adds digital signatures to the DNS, significantly increasing the size of DNS responses. This means DNSSEC is more susceptible to packet fragmentation and makes DNSSEC an attractive vector to abuse in amplification-based denial-of-service attacks. Additionally, key management policies are often complex. This makes DNSSEC fragile and leads to operational failures. In this paper, we argue that the choice for RSA as default cryptosystem in DNSSEC is a major factor in these three problems. Alternative cryptosystems, based on elliptic curve cryptography (ECDSA and EdDSA), exist but are rarely used in DNSSEC. We show that these are highly attractive for use in DNSSEC, although they also have disadvantages. To address these, we have initiated research that aims to investigate the viability of deploying ECC at a large scale in DNSSEC.

On the adoption of the elliptic curve digital signature algorithm (ECDSA) in DNSSEC

The Domain Name System Security Extensions (DNSSEC) are steadily being deployed across the Internet. DNSSEC extends the DNS protocol with two vital security properties, authenticity and integrity, using digital signatures. While DNSSEC is meant to solve security issues in the DNS, it also introduces a new one: the digital signatures significantly increase DNS packet sizes, making DNSSEC an attractive vector to abuse in amplification denial-of-service attacks. By default, DNSSEC uses RSA for digital signatures. Earlier work has shown that alternative signature schemes, based on elliptic curve cryptography, can significantly reduce the impact of signatures on DNS response sizes. In this paper we study the actual adoption of ECDSA by DNSSEC operators, based on longitudinal datasets covering over 50% of the global DNS namespace over a period of 1.5 years. Adoption is still marginal, with just 2.3% of DNSSEC-signed domains in the .com TLD using ECDSA. Nevertheless, use of ECDSA is growing, with at least one large operator leading the pack. And adoption could be up to 42% higher. As we demonstrate, there are barriers to deployment that hamper adoption. Operators wishing to deploy DNSSEC using current recommendations (with ECDSA as signing algorithm) must be mindful of this when planning their deployment.

The Performance Impact of Elliptic Curve Cryptography on DNSSEC Validation

The domain name system (DNS) is a core Internet infrastructure that translates names to machine-readable information, such as IP addresses. Security flaws in DNS led to a major overhaul, with the introduction of the DNS security (DNSSEC) extensions. DNSSEC adds integrity and authenticity to the DNS using digital signatures. DNSSEC, however, has its own concerns. It suffers from availability problems due to packet fragmentation and is a potent source of distributed denial-of-service attacks. In earlier work, we argued that many issues with DNSSEC stem from the choice of RSA as default signature algorithm. A switch to alternatives based on elliptic curve cryptography (ECC) can resolve these issues. Yet switching to ECC introduces a new problem: ECC signature validation is much slower than RSA validation. Thus, switching DNSSEC to ECC imposes a significant additional burden on DNS resolvers, pushing load toward the edges of the network. Therefore, in this paper, we study the question: will switching DNSSEC to ECC lead to problems for DNS resolvers, or can they handle the extra load? To answer this question, we developed a model that accurately predicts how many signature validations DNS resolvers have to perform. This allows us to calculate the additional CPU load ECC imposes on a resolver. Using real-world measurements from four DNS resolvers and with two open-source DNS implementations, we evaluate future scenarios where DNSSEC is universally deployed. Our results conclusively show that switching DNSSEC to ECC signature schemes does not impose an insurmountable load on DNS resolvers, even in worst case scenarios.

The Internet of Names: A DNS Big Dataset

The Domain Name System (DNS) is part of the core infrastructure of the Internet. Tracking changes in the DNS over time provides valuable information about the evolution of the Internets infrastructure. Until now, only one large-scale approach to perform these kinds of measurements existed, passive DNS (pDNS). While pDNS is useful for applications like tracing security incidents, it does not provide sufficient information to reliably track DNS changes over time. We use a complementary approach based on active measurements, which provides a unique, comprehensive dataset on the evolution of DNS over time. Our high-performance infrastructure performs Internet-scale active measurements, currently querying over 50% of the DNS name space on a daily basis. Our infrastructure is designed from the ground up to enable big data analysis approaches on, e.g., a Hadoop cluster. With this novel approach we aim for a quantum leap in DNS-based measurement and analysis of the Internet.

A First Look at Certification Authority Authorization (CAA)

Shaken by severe compromises, the Web’s Public Key Infrastructure has seen the addition of several security mechanisms over recent years. One such mechanism is the Certification Authority Authorization (CAA) DNS record, that gives domain name holders control over which Certification Authorities (CAs) may issue certificates for their domain. First defined in RFC 6844, adoption by the CA/B forum mandates that CAs validate CAA records as of September 8, 2017. The success of CAA hinges on the behavior of three actors: CAs, domain name holders, and DNS operators. We empirically study their behavior, and observe that CAs exhibit patchy adherence in issuance experiments, domain name holders configure CAA records in encouraging but error-prone ways, and only six of the 31 largest DNS operators enable customers to add CAA records. Furthermore, using historic CAA data, we uncover anomalies for already-issued certificates. We disseminated our results in the community. This has already led to specific improvements at several CAs and revocation of mis-issued certificates. Furthermore, in this work, we suggest ways to improve the security impact of CAA. To foster further improvements and to practice reproducible research, we share raw data and analysis tools.