Mechanisms for large-scale vulnerability notifications have been confronted with disappointing remediation rates. It has proven difficult to reach the relevant party and, once reached, to incentivize them to act. We present the first empirical study of a potentially more effective mechanism: Quarantining the vulnerable resource until it is remediated. We have measured the remediation rates achieved by a medium-sized ISP for 1, 688 retail customers running open DNS resolvers or Multicast DNS services. These servers can be abused in UDP-based amplification attacks. We assess the effectiveness of quarantining by comparing remediation with two other groups: One group which was notified but not quarantined and another group where no action was taken. We find very high remediation rates for the quarantined users, 87%, even though they can self-release from the quarantine environment. Of those who received the email-only notification, 76% remediated. Surprisingly, over half of the customers who were not notified at all also remediated, though this is tied to the fact that many observations of vulnerable servers are transient. All in all, quarantining appears more effective than other notification and remediation mechanisms, but it is also clear that it can not be deployed as a general solution for Internet-wide notifications.

Internet security and technology policy research regularly uses technical indicators of abuse to identify culprits and to tailor mitigation strategies. As a major obstacle, current inferences from abuse data that aim to characterize providers with poor security practices often use a naive normalization of abuse (abuse counts divided by network size) and do not take into account other inherent or structural properties of providers. Even the size estimates are subject to measurement errors relating to attribution, aggregation, and various sources of heterogeneity. More precise indicators are costly to measure at Internet scale. We address these issues for the case of hosting providers with a statistical model of the abuse data generation process, using phishing sites in hosting networks as a case study. We decompose error sources and then estimate key parameters of the model, controlling for heterogeneity in size and business model. We find that 84% of the variation in abuse counts across 45,358 hosting providers can be explained with structural factors alone. Informed by the fitted model, we systematically select and enrich a subset of 105 homogeneous “statistical twins” with additional explanatory variables, unreasonable to collect for all hosting providers. We find that abuse is positively associated with the popularity of websites hosted and with the prevalence of popular content management systems. Moreover, hosting providers who charge higher prices (after controlling for level differences between countries) witness less abuse. These structural factors together explain a further 77% of the remaining variation. This calls into question premature inferences from raw abuse indicators about the security efforts of actors, and suggests the adoption of similar analysis frameworks in all domains where network measurement aims at informing technology policy.

To enhance competition and choice in the domain name system, ICANN introduced the new gTLD program, which added hundreds of new gTLDs (e.g. .nyc, .io) to the root DNS zone. While the program arguably increased the range of domain names available to consumers, it might also have created new opportunities for cybercriminals. To investigate that, we present the first comparative study of abuse in the domains registered under the new gTLD program and legacy gTLDs (18 in total, such as .com, .org). We combine historical datasets from various sources, including DNS zone files, WHOIS records, passive and active DNS and HTTP measurements, and 11 reputable abuse feeds to study abuse across gTLDs. We find that the new gTLDs appear to have diverted abuse from the legacy gTLDs: while the total number of domains abused for spam remains stable across gTLDs, we observe a growing number of spam domains in new gTLDs which suggests a shift from legacy gTLDs to new gTLDs. Although legacy gTLDs had a rate of 56.9 spam domains per 10,000 registrations (Q4 2016), new gTLDs experienced a rate of 526.6 in the same period-which is almost one order of magnitude higher. In this study, we also analyze the relationship between DNS abuse, operator security indicators and the structural properties of new gTLDs. The results indicate that there is an inverse correlation between abuse and stricter registration policies. Our findings suggest that cybercriminals increasingly prefer to register, rather than hack, domain names and some new gTLDs have become a magnet for malicious actors. ICANN is currently using these results to review the existing anti-abuse safeguards, evaluate their joint effects and to introduce more effective safeguards before an upcoming new gTLD rollout.

A variety of botnets are used in attacks on financial services. Banks and security firms invest a lot of effort in detecting and combating malware-assisted takeover of customer accounts. A critical resource of these botnets is their command-and-control (C&C) infrastructure. Attackers rent or compromise servers to operate their C&C infrastructure. Hosting providers routinely take down C&C servers, but the effectiveness of this mitigation strategy depends on understanding how attackers select the hosting providers to host their servers. Do they prefer, for example, providers who are slow or unwilling in taking down C&Cs? In this paper, we analyze 7 years of data on the C&C servers of botnets that have engaged in attacks on financial services. Our aim is to understand whether attackers prefer certain types of providers or whether their C&Cs are randomly distributed across the whole attack surface of the hosting industry. We extract a set of structural properties of providers to capture the attack surface. We model the distribution of C&Cs across providers and show that the mere size of the provider can explain around 71% of the variance in the number of C&Cs per provider, whereas the rule of law in the country only explains around 1%. We further observe that price, time in business, popularity and ratio of vulnerable websites of providers relate signi ficantly with C&C counts. Finally, we find that the speed with which providers take down C&C domains has only a weak relation with C&C occurrence rates, adding only 1% explained variance. This suggests attackers have little to no preference for providers who allow long-lived C&C domains.

Over the years cybercriminals have misused the Domain Name System (DNS) - a critical component of the Internet - to gain profit. Despite this persisting trend, little empirical information about the security of Top-Level Domains (TLDs) and of the overall 'health' of the DNS ecosystem exists. In this paper, we present security metrics for this ecosystem and measure the operational values of such metrics using three representative phishing and malware datasets. We benchmark entire TLDs against the rest of the market. We explicitly distinguish these metrics from the idea of measuring security performance, because the measured values are driven by multiple factors, not just by the performance of the particular market player. We consider two types of security metrics: occurrence of abuse and persistence of abuse. In conjunction, they provide a good understanding of the overall health of a TLD. We demonstrate that attackers abuse a variety of free services with good reputation, affecting not only the reputation of those services, but of entire TLDs. We find that, when normalized by size, old TLDs like.com host more bad content than new generic TLDs. We propose a statistical regression model to analyze how the different properties of TLD intermediaries relate to abuse counts. We find that next to TLD size, abuse is positively associated with domain pricing (i.e. registries who provide free domain registrations witness more abuse). Last but not least, we observe a negative relation between the DNSSEC deployment rate and the count of phishing domains.

The 2013 National Security Agency revelations of pervasive monitoring have led to an "encryption rush" across the computer and Internet industry. To push back against massive surveillance and protect users' privacy, vendors, hosting and cloud providers have widely deployed encryption on their hardware, communication links, and applications. As a consequence, most web connections nowadays are encrypted. However, there is still a significant part of Internet traffic that is not encrypted. It has been argued that both costs and complexity associated with obtaining and deploying X.509 certificates are major barriers for widespread encryption, since these certificates are required to establish encrypted connections. To address these issues, the Electronic Frontier Foundation, Mozilla Foundation, the University of Michigan and a number of partners have set up Let's Encrypt (LE), a certificate authority that provides both free X.509 certificates and software that automates the deployment of these certificates. In this paper, we investigate if LE has been successful in democratizing encryption: we analyze certificate issuance in the first year of LE and show from various perspectives that LE adoption has an upward trend and it is in fact being successful in covering the lower-cost end of the hosting market.

Hosting services are associated with various security threats, yet the market has barely been studied empirically. Most security research has relied on routing data and equates providers with Autonomous Systems, ignoring the complexity and heterogeneity of the market. To overcome these limitations, we combined passive DNS data with WHOIS data to identify providers and some of their properties. We found 45,434 hosting providers, spread around a median address space size of 1,517 IP addresses. There is surprisingly little consolidation in the market, even though its services seem amenable to economies of scale. We applied cluster analysis on several measurable characteristics of providers. This uncovered a diverse set of business profiles and an indication of what fraction of the market fits each profile. The profiles are associated with significant differences in security performance, as measured by the uptime of phishing sites. This suggests the approach provides an effective way for security researchers to take the heterogeneity of the market into account.