Biblio

As the Internet becomes an important part of the infrastructure our society depends on, it is crucial to construct networks that are able to work even when part of the network is compromised. This paper presents the first practical intrusion-tolerant network service, targeting high-value applications such as monitoring and control of global clouds and management of critical infrastructure for the power grid. We use an overlay approach to leverage the existing IP infrastructure while providing the required resiliency and timeliness. Our solution overcomes malicious attacks and compromises in both the underlying network infrastructure and in the overlay itself. We deploy and evaluate the intrusion-tolerant overlay implementation on a global cloud spanning East Asia, North America, and Europe, and make it publicly available.

The cloud has become an established and widespread paradigm. This success is due to the gain of flexibility and savings provided by this technology. However, the main obstacle to full cloud adoption is security. The cloud, as many other systems taking advantage of the Internet, is also facing threats that compromise data confidentiality and availability. In addition, new cloud-specific attacks have emerged and current intrusion detection and prevention mechanisms are not enough to protect the complex infrastructure of the cloud from these vulnerabilities. Furthermore, one of the promises of the cloud is the Quality of Service (QoS) by continuous delivery, which must be ensured even in case of intrusion. This work presents an overview of the main cloud vulnerabilities, along with the solutions proposed in the context of the H2020 CLARUS project in terms of monitoring techniques for intrusion detection and prevention, including attack-tolerance mechanisms.

Computer systems face the threat of deliberate security intrusions due to malicious attacks that exploit security holes or vulnerabilities. In practice, these security holes or vulnerabilities still remain in the system and applications even if developers carefully execute system testing. Thus it is necessary and important to develop the mechanism to prevent and/or tolerate security intrusions. As a result, the computer systems are often evaluated with confidentiality, integrity and availability (CIA) criteria from the viewpoint of security, and security is treated as a QoS (Quality of Service) attribute at par with other QoS attributes such as capacity and performance. In this paper, we present the method for quantifying a security attribute called mean time to security failure (MTTSF) of a VM-based intrusion tolerant system based on queueing theory.

Ensuring the integrity and security of the memory system is critical. Recent studies have shown serious security concerns due to "rowhammer" attacks, where repeated accesses to a row of memory cause bit flips in adjacent rows. Recent work by Google's Project Zero has shown how to leverage rowhammer-induced bit-flips as the basis for security exploits that include malicious code injection and memory privilege escalation. Being an important security concern, industry has attempted to defend against rowhammer attacks. Deployed defenses employ two strategies: (1) doubling the system DRAM refresh rate and (2) restricting access to the CLFLUSH instruction that attackers use to bypass the cache to increase memory access frequency (i.e., the rate of rowhammering). We demonstrate that such defenses are inadequte: we implement rowhammer attacks that both avoid using the CLFLUSH instruction and cause bit flips with a doubled refresh rate. Our next-generation CLFLUSH-free rowhammer attack bypasses the cache by manipulating cache replacement state to allow frequent misses out of the last-level cache to DRAM rows of our choosing. To protect existing systems from more advanced rowhammer attacks, we develop a software-based defense, ANVIL, which thwarts all known rowhammer attacks on existing systems. ANVIL detects rowhammer attacks by tracking the locality of DRAM accesses using existing hardware performance counters. Our detector identifies the rows being frequently accessed (i.e., the aggressors), then selectively refreshes the nearby victim rows to prevent hammering. Experiments running on real hardware with the SPEC2006 benchmarks show that ANVIL has less than a 1% false positive rate and an average slowdown of 1%. ANVIL is low-cost and robust, and our experiments indicate that it is an effective approach for protecting existing and future systems from even advanced rowhammer attacks.

Memory disclosure vulnerabilities enable an adversary to successfully mount arbitrary code execution attacks against applications via so-called just-in-time code reuse attacks, even when those applications are fortified with fine-grained address space layout randomization. This attack paradigm requires the adversary to first read the contents of randomized application code, then construct a code reuse payload using that knowledge. In this paper, we show that the recently proposed Execute-no-Read (XnR) technique fails to prevent just-in-time code reuse attacks. Next, we introduce the design and implementation of a novel memory permission primitive, dubbed No-Execute-After-Read (near), that foregoes the problems of XnR and provides strong security guarantees against just-in-time attacks in commodity binaries. Specifically, near allows all code to be disclosed, but prevents any disclosed code from subsequently being executed, thus thwarting just-in-time code reuse. At the same time, commodity binaries with mixed code and data regions still operate correctly, as legitimate data is still readable. To demonstrate the practicality and portability of our approach we implemented prototypes for both Linux and Android on the ARMv8 architecture, as well as a prototype that protects unmodified Microsoft Windows executables and dynamically linked libraries. In addition, our evaluation on the SPEC2006 benchmark demonstrates that our prototype has negligible runtime overhead, making it suitable for practical deployment.

Computer security has become an increasingly important hot topic in computer and communication industry, since it is important to support critical business process and to protect personal and sensitive information. Computer security is to keep security attributes (confidentiality, integrity and availability) of computer systems, which face the threats such as deny-of-service (DoS), virus and intrusion. To ensure high computer security, the intrusion tolerance technique based on fault-tolerant scheme has been widely applied. This paper presents the quantitative performance evaluation of a virtual machine (VM) based intrusion tolerant system. Concretely, two security measures are derived; MTTSF (mean time to security failure) and the effective traffic intensity. The mathematical analysis is achieved by using Laplace-Stieltjes transforms according to the analysis of M/G/1 queueing system.

Today's mobile app economy has greatly expanded the types of "things" people can share –- spanning from new types of digital content like physiological data (e.g., workouts) to physical things like apartments and work tools ("sharing economy"). To understand whether mobile platforms provide adequate support for such novel sharing services, we surveyed 200 participants about their experiences with six types of emergent sharing services. For each domain we elicited device usage practices and identified corresponding device selection criteria. Our analysis suggests that, despite contemporary mobile first design efforts, desktop interfaces of emergent content sharing services are often considered more efficient and easier to use –- both for sharing and access control tasks (i.e., privacy). Based on our findings, we outline device-related design and research opportunities in this space.

Physical Unclonable Functions (PUFs) measure manufacturing variations inside integrated circuits to derive internal secrets during run-time and avoid to store secrets permanently in non-volatile memory. PUF responses are noisy such that they require error correction to generate reliable cryptographic keys. To date, when needed one single key is reproduced in the field and always used, regardless of its reliability. In this work, we compute online reliability information for a reproduced key and perform multiple PUF readout and error correction steps in case of an unreliable result. This permits to choose the most reliable key among multiple derived key candidates with different corrected error patterns. We achieve the same average key error probability from less PUF response bits with this approach. Our proof of concept design for a popular reference scenario uses Differential Sequence Coding (DSC) and a Viterbi decoder with reliability output information. It requires 39% less PUF response bits and 16% less helper data bits than the regular approach without the option for multiple readouts.

This paper introduces typy, a statically typed programming language embedded by reflection into Python. typy features a fragmentary semantics, i.e. it delegates semantic control over each term, drawn from Python's fixed concrete and abstract syntax, to some contextually relevant user-defined semantic fragment. The delegated fragment programmatically 1) typechecks the term (following a bidirectional protocol); and 2) assigns dynamic meaning to the term by computing a translation to Python. We argue that this design is expressive with examples of fragments that express the static and dynamic semantics of 1) functional records; 2) labeled sums (with nested pattern matching a la ML); 3) a variation on JavaScript's prototypal object system; and 4) typed foreign interfaces to Python and OpenCL. These semantic structures are, or would need to be, defined primitively in conventionally structured languages. We further argue that this design is compositionally well-behaved. It avoids the expression problem and the problems of grammar composition because the syntax is fixed. Moreover, programs are semantically stable under fragment composition (i.e. defining a new fragment will not change the meaning of existing program components.)

The serializability of transactions is the most important property that ensure correct processing to transactions. In case of concurrent access to the same data by several transactions, or in case of dependency relationships between running sub transactions. But some transactions has been marked as malicious and they compromise the serialization of running system. For that purpose, we propose an intrusion tolerant scheme to ensure the continuity of the running transactions. A transaction dependency graph is also used by the CDC to make decisions concerning the set of data and transactions that are threatened by a malicious activity. We will give explanations about how to use the proposed scheme to illustrate its behavior and efficiency against a compromised transaction-based in a cloud of databases environment. Several issues should be considered when dealing with the processing of a set of interleaved transactions in a transaction based environment. In most cases, these issues are due to the concurrent access to the same data by several transactions or the dependency relationship between running transactions. The serializability may be affected if a transaction that belongs to the processing node is compromised.

Recent data breaches in domains such as healthcare, where confidentiality of data is crucial, indicate that misuse cases often originate from user errors rather than vulnerabilities in the technical (software or hardware) architecture. Current requirements engineering (RE) approaches determine what access control mechanisms are needed to protect sensitive resources. However, current RE approaches inadequately characterize how a user is expected to interact with others in relation to the relevant resources. Consequently, a requirements analyst cannot readily identify the vulnerabilities based on user interactions. We adopt social norms as a natural, formal means of characterizing user interactions wherein potential misuses map to norm violations. Our research goal is to help analysts identify misuse cases by systematically generating potential temporal enactments that violate formally stated social norms. We propose Nane: a formal framework for identifying misuse cases from norm enactments. We represent misuse cases formally, and propose a semiautomated process for identifying misuse cases based on norm enactments. We show that our process is sound and complete with respect to the stated norms. We discuss the expressiveness of our representation, and demonstrate how Nane enables monitoring of misuse cases via temporal reasoning.

Privacy remains a major challenge today partly because it brings together social and technical considerations. Yet, current software engineering focuses only on the technical aspects. In contrast, our approach, Revani, understands privacy from the standpoint of sociotechnical systems (STSs), with particular attention on the social elements of STSs. We specify STSs via a combination of technical mechanisms and social norms founded on accountability.

Revani provides a way to formally represent mechanisms and norms, and applies model checking to verify whether specified mechanisms and norms would satisfy the requirements of the stakeholders. Additionally, Revani provides a set of design patterns and a revision tool to update an STS specification as necessary. We demonstrate the working of Revani on a healthcare emergency use case pertaining to disasters.

Syntax extension mechanisms are powerful, but reasoning about syntax extensions can be difficult. Recent work on type-specific languages (TSLs) addressed reasoning about composition, hygiene and typing for extensions introducing new literal forms. We supplement TSLs with typed syntax macros (TSMs), which, unlike TSLs, are explicitly invoked to give meaning to delimited segments of arbitrary syntax. To maintain a typing discipline, we describe two avors of term-level TSMs: synthetic TSMs specify the type of term that they generate, while analytic TSMs can generate terms of arbitrary type, but can only be used in positions where the type is otherwise known. At the level of types, we describe a third avor of TSM that generates a type of a specified kind along with its TSL and show interesting use cases where the two mechanisms operate in concert.

Since the late 1990s the sales of processors targeted for embedded systems has exceeded sales for the PC market. Some embedded systems tightly link the computing resources to the physical world. Such systems are called cyber-physical systems. Autonomous cyber-physical systems often have safety-critical missions, which means they must be fault tolerant. Unfortunately fault recovery options are limited; adapting the physical system behavior may be the only viable option. Consequently, autonomous cyber-physical systems are a class of adaptive systems. The evolvable hardware field has developed a number of techniques that should prove to be useful for designing cyber-physical systems although work along those lines has only recently begun. In this paper we provide an overview of cyber-physical systems and then describe how two evolvable hardware techniques can be used to adapt the physical system behavior in real-time. The goal is to introduce cyber-physical systems to the evolvable hardware community and encourage those researchers to begin working in this emerging field.

Optical Coherence Tomography (OCT) has shown a great potential as a complementary imaging tool in the diagnosis of skin diseases. Speckle noise is the most prominent artifact present in OCT images and could limit the interpretation and detection capabilities. In this work we evaluate various denoising filters with high edge-preserving potential for the reduction of speckle noise in 256 dermatological OCT B-scans. Our results show that the Enhanced Sigma Filter and the Block Matching 3-D (BM3D) as 2D denoising filters and the Wavelet Multiframe algorithm considering adjacent B-scans achieved the best results in terms of the enhancement quality metrics used. Our results suggest that a combination of 2D filtering followed by a wavelet based compounding algorithm may significantly reduce speckle, increasing signal-to-noise and contrast-to-noise ratios, without the need of extra acquisitions of the same frame.

Experience influences actions people take in protecting themselves against phishing. One way to measure experience is through mental models. Mental models are internal representations of a concept or system that develop with experience. By rating pairs of concepts on the strength of their relationship, networks can be created through Pathfinder, showing an in-depth analysis of how information is organized. Researchers had novice and expert computer users rate three sets of terms related to phishing. The terms were divided into three categories: prevention of phishing, trends and characteristics of phishing attacks, and the consequences of phishing. Results indicated that expert mental models were more complex with more links between concepts. Specifically, experts had sixteen, thirteen, and fifteen links in the networks describing the prevention, trends, and consequences of phishing, respectively; however, novices only had eleven, nine, and nine links in the networks describing prevention, trends, and consequences of phishing, respectively. These preliminary results provide quantifiable network displays of mental models of novices and experts that cannot be seen through interviews. This information could provide a basis for future research on how mental models could be used to determine phishing vulnerability and the effectiveness of phishing training.