The Domain Name System (DNS) is responsible for mapping human readable domain names to internet protocol (IP) addresses. DNS is a ubiquitous part of internet and intranet communication, making it a convenient and comprehensive source for data to infer network health, performance, and security. A victim of its own success, monitoring real-time DNS traffic is a challenge due to sheer volume: huge amounts of DNS packets flow through a typical enterprise in a single day. In this paper, we describe eyeDNS, a scalable and extensible system for near real-time aggregation, storage, analysis, and visualization of DNS traffic collected by a hardware back-end. We report on eyeDNS's deployment and data collection on a large public university's network over a timeframe of 15 months. Moreover, we leveraged data from the following 6 months to validate findings made during the initial timeframe. With fast query response, aggregation, and visualization of DNS data, eyeDNS helped identify instances of anomalous network use, malware-specific behaviors, and scamming activities. eyeDNS is currently being used by the university's security personnel and has demonstrated its effectiveness in extracting trends and outliers from large volumes of DNS data collected from a diverse environment, where even commercial tools struggle to provide timely and actionable analysis.

Abstract We describe SYM-GOTR, a protocol for secure Group Off-The-Record (GOTR) messaging. In contrast to previous work, SYM-GOTR is the first protocol to offer confidential, authenticated, and repudiable conversations among a dynamic group with the additional properties of message unlinkability and the guarantee that all users see the same conversation, while providing efficient use of network and CPU resources. SYM-GOTR achieves these properties through the use of a novel optimistic consistency check protocol that either determines that all users agree on a transcript with constant-size messages or identifies at least one user that has not followed the protocol. We provide an implementation of SYM-GOTR as a Java library along with a plugin for the Jitsi instant messaging client. We analyze the performance of SYM-GOTR in a real world deployment scenario and discuss the challenges of providing a usable implementation without compromising the security of the conversation.

Safety-critical system engineering and traditional safety analyses have for decades been focused on problems caused by natural or accidental phenomena. Security analyses, on the other hand, focus on preventing intentional, malicious acts that reduce system availability, degrade user privacy, or enable unauthorized access. In the context of safety-critical systems, safety and security are intertwined, e.g., injecting malicious control commands may lead to system actuation that causes harm. Despite this intertwining, safety and security concerns have traditionally been designed and analyzed independently of one another, and examined in very different ways. In this work we examine a new hazard analysis technique---Systematic Analysis of Faults and Errors (SAFE)---and its deep integration of safety and security concerns. This is achieved by explicitly incorporating a semantic framework of error "effects" that unifies an adversary model long used in security contexts with a fault/error categorization that aligns with previous approaches to hazard analysis. This categorization enables analysts to separate the immediate, component-level effects of errors from their cause or precise deviation from specification.

In the Bitcoin system, participants are rewarded for solving cryptographic puzzles. In order to receive more consistent rewards over time, some participants organize mining pools and split the rewards from the pool in proportion to each participant's contribution. However, several attacks threaten the ability to participate in pools. The block withholding (BWH) attack makes the pool reward system unfair by letting malicious participants receive unearned wages while only pretending to contribute work. When two pools launch BWH attacks against each other, they encounter the miner's dilemma: in a Nash equilibrium, the revenue of both pools is diminished. In another attack called selfish mining, an attacker can unfairly earn extra rewards by deliberately generating forks.

Security attacks on medical devices have been shown to have potential safety concerns. Because of this, stakeholders (device makers, regulators, users, etc.) have increasing interest in enhancing security in medical devices. An effective means to approach this objective is to integrate systematic security requirements elicitation and analysis into the design and evaluation of medical device software. This paper extends the sequence-based enumeration approach, a systematic approach for defining the behavior of embedded software, to analyze the requirement documents of a medical device for the purpose of eliciting security requirements. As a proof of concept, we apply our approach on a concrete case study, which shows that the extended approach is useful for identifying sequences of medical device events that might be harmful to the patient, for example because the events are initiated by an active adversary trying to use the device in a malicious way. We then show how security requirements may be formulated based on the identified threats. By exploring these sequences systematically, the developers can reliably assess what, where, and how the security threats may manifest in their system, what the safety implications are, and finally they can evaluate the resulting requirements and mitigations.

Robust authentication and authorization are vital to next-generation distributed medical systems - the Medical Internet of Things (MIoT). However, there is yet no good authorization model for real-time multi-channel data from systems of heterogeneous devices providing multiple physiological parameters for clinicians who may change on a minute-by-minute basis. We present a flexible authorization architecture for interoperable medical systems, and an implementation and evaluation in the context of the Medical Device Coordination Framework (MDCF) high-assurance middleware.

This paper presents PIVOT, a new flow fingerprinting scheme for identifying websites visited by a user of a low-latency anonymous communication system. The adversary is difficult to detect, as data collection is fully passive and can be performed at the server-side, client-side, or anywhere along the packet path. Further, data analysis can be performed in real time or offline, as long as flow information can be stored. The fingerprint is composed of a combination of traffic volume and timing information, and can be represented and stored in a compact format. PIVOT can be implemented using weaker adversary models than previous fingerprinting schemes and can identify websites within a multi-website browsing session, i.e., the user is vulnerable even when employing cover traffic and/or browsing multiple websites. The design is efficient, easy to implement, requires only passive network monitoring, and is robust to most active defenses against flow fingerprinting, additional bandwidth utilization by the user, as well as alteration in packet size and packet frequency introduced by one-hop anonymizing proxies or multi-hop anonymity systems such as Tor. We implement PIVOT and validate its accuracy against the Anonymizer.com one-hop proxy and the Tor browser bundle, using browsing patterns that better match real human behavior than those in the previous literature. Results indicate that end-to-end unlinkability can be broken with modest processing power and network capacity requirements, even if the target flow has been repacketized and combined with other flows.

We present our experiences and outcomes from a programming camp held for sixth through ninth grade students. The instructional team included five pre-service teachers who earned field experience credit for this work, and one in-service teacher. The pre-service teachers were art and music teachers-in-training, providing an opportunity for us to utilize their creative expertise in developing content for the camp. In turn, we helped the teachers explore ways they might incorporate today's user-friendly programming environments (in this case, Scratch) into their curriculum. During each of four week-long sessions, the pre-service teachers gradually took over more teaching responsibilities, modifying and then presenting lessons that incorporate their own music and art expertise into the programming activities.

Non-use or incorrect use of security software is one major reason for privacy breaches of all scales. The problem is compounded by software, security policies, and user interfaces that are difficult to use and understand. Using widely accepted user interface analysis methods, we examine a popular free and open source disk encryption software package, and find that it is far from accessible to ordinary users. Using rigorous interface design principles, we derive several concrete changes that would make the software easier to use, and construct a new interface to test our theories. We evaluate the two interfaces through a randomized user study in a controlled laboratory setting, and determine that the new interface is significantly easier to understand and faster to use, especially for novice computer users. We observe not only measurable speed-ups of common tasks, but also improved user-reported ease of use ratings. Several of our design choices turn out to have been misguided, making some tasks more difficult in our modified interface, but fortunately our alterations are mutually independent, i.e. reverting some components to their original design does not nullify the benefit of other modifications. Our experience shows that even simple, intuitive, and logically consistent modifications to complex interfaces have dramatic positive usability effects, and can be easily applied to different pieces of security software in order to reduce the impediment to uptake by novice users.

Encounter-based social networks and encounter-based systems link users who share a location at the same time, as opposed to the traditional social network paradigm of linking users who have an offline friendship. This new approach presents challenges that are fundamentally different from those tackled by previous social network designs. In this paper, we explore the functional and security requirements for these new systems, such as availability, security, and privacy, and present several design options for building secure encounter-based social networks. To highlight these challenges, we examine one recently proposed encounter-based social network design and compare it to a set of idealized security and functionality requirements. We show that it is vulnerable to several attacks, including impersonation, collusion, and privacy breaching, even though it was designed specifically for security. Mindful of the possible pitfalls, we construct a flexible framework for secure encounter-based social networks, which can be used to construct networks that offer different security, privacy, and availability guarantees. We describe two example constructions derived from this framework, and consider each in terms of the ideal requirements. Some of our new designs fulfill more requirements in terms of system security, reliability, and privacy than previous work. We also evaluate real-world performance of one of our designs by implementing a proof-of-concept iPhone application called MeetUp. Experiments highlight the potential of our system and hint at the deployability of our designs on a large scale.

Ad hoc low-power wireless networks are an exciting research direction in sensing and pervasive computing. Prior security work in this area has focused primarily on denial of communication at the routing or medium access control levels. This paper explores resource depletion attacks at the routing protocol layer, which permanently disable networks by quickly draining nodes' battery power. These "Vampire” attacks are not specific to any specific protocol, but rather rely on the properties of many popular classes of routing protocols. We find that all examined protocols are susceptible to Vampire attacks, which are devastating, difficult to detect, and are easy to carry out using as few as one malicious insider sending only protocol-compliant messages. In the worst case, a single Vampire can increase network-wide energy usage by a factor of O(N), where N in the number of network nodes. We discuss methods to mitigate these types of attacks, including a new proof-of-concept protocol that provably bounds the damage caused by Vampires during the packet forwarding phase.

In this paper we outline requirements, challenges, and designs for encounter-based mobile social networks, where relationships are based on a temporarily shared location. To illustrate the challenges we examine a recently proposed design, SMILE, against a set of functional and security requirements. We show that SMILE is vulnerable to several attacks such as impersonation, collusion, and privacy breaching, even though it was built with the explicit goal of resisting some of those attacks. With this in mind, we construct a flexible framework for secure mobile social networks, and describe how to use it in order to construct several networks which offer somewhat different security properties. Each of the designs is then examined against the ideal requirements where some are shown to outperform previous work.

In this work, we introduce the Coordinated Cross Plane Session Termination, or CXPST, attack, a distributed denial of service attack that attacks the control plane of the Internet. CXPST extends previous work that demonstrates a vulnerability in routers that allows an adversary to disconnect a pair of routers using only data plane traffic. By carefully choosing BGP sessions to terminate, CXPST generates a surge of BGP updates that are seen by nearly all core routers on the Internet. This surge of updates surpasses the computational capacity of affected routers, crippling their ability to make routing decisions

Low-latency anonymity systems such as Tor, AN.ON, Crowds, and Anonymizer.com aim to provide anonymous connections that are both untraceable by “local” adversaries who control only a few machines and have low enough delay to support anonymous use of network services like Web browsing and remote login. One consequence of these goals is that these services leak some information about the network latency between the sender and one or more nodes in the system. We present two attacks on low-latency anonymity schemes using this information. The first attack allows a pair of colluding Web sites to predict, based on local timing information and with no additional resources, whether two connections from the same Tor exit node are using the same circuit with high confidence. The second attack requires more resources but allows a malicious Web site to gain several bits of information about a client each time he visits the site. We evaluate both attacks against two low-latency anonymity protocols—the Tor network and the MultiProxy proxy aggregator service—and conclude that both are highly vulnerable to these attacks.

We introduce the concept of membership-concealing overlay networks (MCONs), which hide the real-world identities of participants. We argue that while membership concealment is orthogonal to anonymity and censorship resistance, pseudonymous communication and censorship resistance become much easier if done over a membership-concealing network. We formalize the concept of membership concealment, discuss a number of attacks against existing systems and present real-world attack results. We then propose three proof-of-concept MCON designs that resist those attacks: one that is more efficient, another that is more robust to membership churn, and a third that balances efficiency and robustness. We show theoretical and simulation results demonstrating the feasibility and performance of our schemes.

Low-latency anonymity systems such as Tor, AN.ON, Crowds, and Anonymizer.com aim to provide anonymous connections that are both untraceable by "local" adversaries who control only a few machines, and have low enough delay to support anonymous use of network services like web browsing and remote login. One consequence of these goals is that these services leak some information about the network latency between the sender and one or more nodes in the system. This paper reports on three experiments that partially measure the extent to which such leakage can compromise anonymity. First, using a public dataset of pairwise round-trip times (RTTs) between 2000 Internet hosts, we estimate that on average, knowing the network location of host A and the RTT to host B leaks 3.64 bits of information about the network location of B. Second, we describe an attack that allows a pair of colluding web sites to predict, based on local timing information and with no additional resources, whether two connections from the same Tor exit node are using the same circuit with 17% equal error rate. Finally, we describe an attack that allows a malicious website, with access to a network coordinate system and one corrupted Tor router, to recover roughly 6.8 bits of network location per hour.

An electronic cash system allows users to withdraw coins, represented as bit strings, from a bank or broker, and spend those coins anonymously at participating merchants, so that the broker cannot link spent coins to the user who withdraws them. A variety of schemes with various security properties have been proposed for this purpose, but because strings of bits are inherently copyable, they must all deal with the problem of double-spending. In this paper, we present an electronic cash scheme that introduces a new peer-to-peer system architecture to prevent double-spending without requiring an on-line trusted party or tamper-resistant software or hardware. The scheme is easy to implement, computationally efficient, and provably secure. To demonstrate this, we report on a proof-of-concept implementation for Internet vendors along with a detailed complexity analysis and selected security proofs.