Cyber-physical systems and their smart components have a pervasive presence in all our daily activities. Unfortunately, identifying the potential threats and issues in these systems and selecting enough protection is challenging given that such environments combine human, physical and cyber aspects to the system design and implementation. Current threat models and analysis do not take into consideration all three aspects of the analyzed system, how they can introduce new vulnerabilities or protection measures to each other. In this work, we introduce a novel threat model for cyber-physical systems that combines the cyber, physical, and human aspects. Our model represents the system's components relations and security properties by taking into consideration these three aspects. Together with the threat model we also propose a threat analysis method that allows understanding the security state of the system's components. The threat model and the threat analysis have been implemented into an automatic tool, called TAMELESS, that automatically analyzes threats to the system, verifies its security properties, and generates a graphical representation, useful for security architects to identify the proper prevention/mitigation solutions. We show and prove the use of our threat model and analysis with three cases studies from different sectors.

In this paper, we describe an efficient methodology to guide investigators during network forensic analysis. To this end, we introduce the concept of core attack graph, a compact representation of the main routes an attacker can take towards specific network targets. Such compactness allows forensic investigators to focus their efforts on critical nodes that are more likely to be part of attack paths, thus reducing the overall number of nodes (devices, network privileges) that need to be examined. Nevertheless, core graphs also allow investigators to hierarchically explore the graph in order to retrieve different levels of summarised information. We have evaluated our approach over different network topologies varying parameters such as network size, density, and forensic evaluation threshold. Our results demonstrate that we can achieve the same level of accuracy provided by standard logical attack graphs while significantly reducing the exploration rate of the network.

Attestation and measurements inspection are different but complementary approaches towards the same goal: ascertaining the integrity of sensor nodes in wireless sensor networks. In this paper we compare the benefits and drawbacks of both techniques and seek to determine how to best combine them. However, our study shows that no single solution exists, as each choice introduces changes in the measurements collection process, affects the attestation protocol, and gives a different balance between the high detection rate of attestation and the low power overhead of measurements inspection. Therefore, we propose three strategies that combine measurements inspection and attestation in different ways, and a way to choose between them based on the requirements of different applications. We analyse their performance both analytically and in a simulator. The results show that the combined strategies can achieve a detection rate close to attestation, in the range 96--99%, whilst keeping a power overhead close to measurements inspection, in the range 1--10%.

It is a mistake to assume that each embedded object in the Internet of Things will implement a TCP/IP stack similar to those present in contemporary operating systems. Typical requirements of ordinary things, such as low power consumption, small size, and low cost, demand innovative solutions. In this article, we describe the design, implementation, and evaluation of a trustful infrastructure for the Internet of Things based on EPOSMote. The infrastructure was built around EPOS' second generation of motes, which features an ARM processor and an IEEE 802.15.4 radio transceiver. It is presented to end users through a trustful communication protocol stack compatible with TCP/IP. Trustfulness was tackled at MAC level by extending C-MAC, EPOS native MAC protocol, with AES capabilities that were used to encrypt and authenticate IP datagrams packets. Our authentication mechanism encompasses temporal information to protect the network against replay attacks. The prototype implementation was assessed for processing, memory, and energy consumption with positive results.

Receiver-based MAC (RB-MAC) is a preamble-sampling MAC protocol for WSNs in which a receiver node is dynamically elected, among potential neighbors of the sender node, based on current channel conditions. In this paper, we evaluate the performance of RB-MAC and compare it with a senderbased preamble-sampling MAC protocol by using analytical methods, and implementation in real sensor nodes. We have used Configurable MAC (C-MAC), which is a framework to develop different MAC protocols in WSNs. This framework is realized as a component architecture that can produce application-specific communication protocols. The experimental results presented in the paper corroborate with the analytical and numerical results showing how RB-MAC outperforms sender-based MAC protocols in terms of transmission delay, and energy consumption.

WSNs, despite of its limited resources, are expected to operate without human interventions for a long period of time. Nevertheless, the environment might develop unpredicted characteristics or some network functionality might need some changes. Thus, it is necessary a mechanism which allows software reprogramming of the network nodes after its deployment. This paper presents the integration of a data dissemination protocol and ELUS, an OS support environment. The dissemination protocol is responsible for spreading the data across the network, while ELUS isolates the system components in memory position independent units, allowing their updating at execution time. We have evaluated our infrastructure, using real sensor nodes, in terms of memory consumption, dissemination, and reprogramming time.

This article describes the design, implementation and evaluation of a trustful infrastructure for the Internet of Things (IoT) based on EPOS Mote. The infrastructure was built around EPOS' second generation of motes, which features an ARM processor and an IEEE 802.15.4 radio transceiver. It is presented to end users through a trustful communication protocol stack compatible with TCP/IP. Trustfulness was tackled at MAC level by extending C-MAC, EPOS native MAC protocol, with Advanced Encryption Standard (AES) capabilities that were subsequently used to encrypt and authenticate packets containing IP data grams. Our authentication mechanism encompasses temporal information to protect the network against replay attacks. The infrastructure was designed bearing in mind the severe resource limitation typical of IoT devices. The prototype implementation was assessed for processing, memory, and energy consumption and strongly confirmed our assumptions.