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Abstract Adversaries may target alerting alarms raised by PLCs (Programmable Logic Controllers) to prevent notifying operators of critical conditions, to hide faults, to disrupt operations, to cause damages to ICS (Industrial Control Systems) and surrounding environment, or to lead to financial loss. The paper focuses on exposing vulnerabilities of the ladder logic code that handles the alerting alarm messages and how to mitigate them. A real-time test bed of a PLC alarms code was developed and used to conduct several stealthy attack techniques to suppress or hinder alarms by exploiting code vulnerabilities. A novel ladder logic solution that consists of countermeasures against the introduced attacks was proposed, demonstrated, and tested. The countermeasure techniques, such as scan time and heartbeat techniques, were able to detect and prevent the code vulnerabilities and other abnormalities. The provided countermeasure techniques in this experiment could be applied to any PLC to enhance the validity and security of its PLC alarms code. Article Highlights Four stealthy attack models were introduced to exploit PLC alarms code. They were embedded to skip, delete, fake out, or delay alerting alarms. Real-time countermeasure solutions with different techniques were introduced: scan time code, heartbeat code, and physical plausibility check. They effectively detected and prevented the introduced attack models. PLC alarms Code general abnormalities was validated and detected using scan time techniques. A list of general best code practices for PLC alarms code was introduced to mitigate code vulnerabilities.

This paper proposes a novel Quality of experience based Energy Efficient method (QEE) to distribute Peer-to-Peer (P2P) video in a mobile ad hoc network. P2P video distribution is first formulated as a resource allocation problem with the aim of maximizing the end user’s quality of experience. We studied the resource allocation problem as a linear optimization problem to provide efficient utilization of upload bandwidth and energy at each mobile node. Furthermore, scalable video coding is used, that helps maximizing the quality of experience by distributing the layered video over multiple sources using multiple paths to minimize the power consumption and the upload bandwidth at each node. The simulation results show that in the case of 10% uploader nodes in the network, and at the nodes velocity of 1 m/s; QEE method consumes 5 to 25% less power, as compared to existing methods such as; EVAN (Energy aware video streaming in wireless ad hoc network), WCNC (Assessing best strategy for adaptive streaming in mobile ad hoc network), QNE (QoE based non Energy Efficient) and NQNE (Non QoE based Non Energy Efficient). This is because the load is efficiently distributed across multiple sources in the network. Furthermore, the result also shows that for the case of 10% uploader nodes in the network QEE method achieves 10% higher Mean Opinion Score (MOS) among nodes as compared to EVAN and QNE methods as it considers path utility for streaming the video using multiple sources over multiple paths. We have also evaluated the performance of QEE under network churn and flash crown scenarios; the result shows that QEE maintains a reasonable quality under such situations.

This paper provides a review of the state-of-the-art of major Programmable Logic Controller (PLC) based devices along with their security concerns. It discusses, mainly, the threats and vulnerabilities of PLCs and associated field devices—including local industrial networks. As PLC-BS are becoming more integrated and interconnected with other complex systems and open source solutions, they are becoming more vulnerable to critical threats and exploitations. Little attention and progress have been made in securing such devices if compared to that of securing overall Industrial Control Systems. This review shows the fact that major PLC based devices have several vulnerabilities and are insecure by design—firmware, code, or hardware. This paper suggests policies, recommendations, and countermeasures to secure PLC-BS. Securing PLC-BS is vital and crucial since a compromised PLC-BS would lead to significant financial loss and safety risks that could endanger human lives or the environment.

A key advance in enabling higher wireless mesh network capacity is allowing routers to transmit or receive (MTR) from multiple neighbors simultaneously over the same frequency. Achieving this capacity, however, is predicated on a link scheduler that is able to capitalize on the MTR capability of nodes to activate the maximum number of active links, and also to derive the shortest schedule that ensures all links are activated at least once. To date, existing schedulers do not consider the transmission or air-time of packet(s). Henceforth, this paper fills this gap and propose to derive the shortest superframe length, defined as the end time of the last transmitting link. Our scheduler, called A-TxRx, greedily adds links whenever a link finishes its transmission. As a result, unlike previous schedulers, links can start transmitting/receiving as soon as there is no conflict. We have evaluated the performance of A-TxRx in various network configurations, and compared it against two state-of-the-art approaches: 2P and JazzyMAC. The results show A-TxRx outperforming these algorithms significantly, especially when the network becomes denser. Specifically, the superframe length of A-TxRx is typically less than half of 2P and JazzyMAC, with 60 % more concurrently transmitting links.

We propose an algorithm that exploits the properties of Scalable Video Coding (SVC) in order to minimize the upload bandwidth at each peer. More specifically, we propose streaming different layers of the same video from different peers. The paper defines an optimization problem to handle the upload bandwidth at each peer. However, the solution to the proposed problem is NP complete. Therefore, we propose an approximation algorithm to solve this problem. In addition, seed servers are introduced in order to deal with extra load in the network. The proposed method provides better performance as compared to the current approaches that use single layer video in combination with SVC. We have compared our simulation results with the model proposed in Shabnam and Mohamed (2010). The simulation results show that the proposed model improves diversity, increases average video quality, reduces the effect of churn and manages flash crowds.

Broadcast is a fundamental operation in wireless sensor networks (WSNs). Given a source node with a packet to broadcast, the aim is to propagate the packet to all nodes in a collision free manner whilst incurring minimum latency. This problem, called minimum latency broadcast scheduling (MLBS), has been studied extensively in wireless ad-hoc networks whereby nodes remain on all the time, and has been shown to be NP-hard. However, only a few studies have addressed this problem in the context of duty-cycled WSNs. In these WSNs, nodes do not wake-up simultaneously, and hence, not all neighbors of a transmitting node will receive a broadcast packet at the same time. Unfortunately, the problem remains NP-hard and multiple transmissions may be necessary due to different wake-up times. Henceforth, this paper considers MLBS in duty cycled WSNs and presents two approximation algorithms, BS-1 and BS-2, that produce a maximum latency of at most $$(\Delta -1) TH$$ ( Δ - 1 ) T H and $$13TH$$ 13 T H respectively. Here, $$\Delta$$ Δ is the maximum degree of nodes, $$T$$ T denotes the number of time slots in a scheduling period, and $$H$$ H is the broadcast latency lower bound obtained from the shortest path algorithm. We evaluated our algorithms under different network configurations and confirmed that the latencies achieved by our algorithms are much lower than existing schemes. In particular, compared to OTAB, the best broadcast scheduling algorithm to date, the broadcast latency and transmission times achieved by BS-1 is at least $$\frac{1}{17}$$ 1 17 and $$\frac{2}{5}$$ 2 5 that of OTAB respectively.

Asynchronous duty cycle Medium Access Control (MAC) protocols do not require global synchronization because nodes determine their wake-up schedule independently. As a result, these MACs have superior performance to those that employ synchronous duty-cycles in terms of energy expenditure, and advantageously, they are simple to implement. A key limitation is that they do not support efficient broadcast. A node needs to transmit a broadcast packet multiple times via unicast because only a subset of its neighbors may be awake at any given point in time. To address this problem, this paper proposes a centralized and distributed asynchronous broadcast algorithm that achieves minimal broadcast latency and redundancy. In addition, it uses a novel asynchronous MAC protocol that ensures all neighbors of a broadcasting node are awake to receive a broadcast. The performance of our algorithms is evaluated under different network configurations. We show via extensive simulation studies that our algorithms have near optimal network performance in terms of broadcast latency. In particular, compared to OTAB, the best broadcast scheduling algorithm to date, the broadcast latency and transmission times achieved by our designs are 1/5 and 1/2 that of OTAB, respectively.