The shared nature of the medium in wireless networks makes it easy for an adversary to launch a Wireless Denial of Service (WDoS) attack. Recent studies, demonstrate that such attacks can be very ...easily accomplished using off-the-shelf equipment. To give a simple example, a malicious node can continually transmit a radio signal in order to block any legitimate access to the medium and/or interfere with reception. This act is called jamming and the malicious nodes are referred to as jammers. Jamming techniques vary from simple ones based on the continual transmission of interference signals, to more sophisticated attacks that aim at exploiting vulnerabilities of the particular protocol used. In this survey, we present a detailed up-to-date discussion on the jamming attacks recorded in the literature. We also describe various techniques proposed for detecting the presence of jammers. Finally, we survey numerous mechanisms which attempt to protect the network from jamming attacks. We conclude with a summary and by suggesting future directions.
Cooperative diversity facilitates spatio-temporal communications without requiring the deployment of physical antenna arrays. While physical layer studies on cooperative diversity have been ...extensive, higher layer protocols which translate the achievable reduction in the SNR per bit for a given target BER, into system wide performance enhancements are yet to mature. The challenge is that appropriate higher layer functions are needed in order to enable cooperative diversity at the physical layer. We focus on network-wide broadcasting with the use of cooperative diversity in ad hoc networks. We design a novel distributed network-wide broadcasting protocol that takes into account the physical layer dependencies that arise with cooperative diversity. We perform extensive simulations that show that our protocol can outperform the best of the noncooperative broadcasting protocols by: (a) achieving up to a threefold increase in network coverage and, (b) by decreasing the latency incurred during the broadcast by about 50%. We also construct an analytical model that captures the behavior of our protocol. Furthermore, we show that computing the optimal solution to the cooperative broadcast problem is NP-complete and construct centralized approximation algorithms. Specifically, we construct an O(N epsi )-approximation algorithm with a computational complexity of O(N4/epsi); we also construct a simpler greedy algorithm.. The costs incurred with these algorithms serve as benchmarks with which one can compare that achieved by any distributed protocol
Cloud-based radio access networks (C-RAN) have been proposed as a cost-efficient way of deploying small cells. Unlike conventional RANs, a C-RAN decouples the baseband processing unit (BBU) from the ...remote radio head (RRH), allowing for centralized operation of BBUs and scalable deployment of light-weight RRHs as small cells. In this work, we argue that the intelligent configuration of the front-haul network between the BBUs and RRHs, is essential in delivering the performance and energy benefits to the RAN and the BBU pool, respectively. We propose FluidNet-a scalable, light-weight framework for realizing the full potential of C-RAN. FluidNet deploys a logically re-configurable front-haul to apply appropriate transmission strategies in different parts of the network and hence cater effectively to both heterogeneous user profiles and dynamic traffic load patterns. FluidNet's algorithms determine configurations that maximize the traffic demand satisfied on the RAN, while simultaneously optimizing the compute resource usage in the BBU pool. We prototype FluidNet on a 6 BBU, 6 RRH WiMAX C-RAN testbed. Prototype evaluations and large-scale simulations reveal that FluidNet's ability to re-configure its front-haul and tailor transmission strategies provides a 50% improvement in satisfying traffic demands, while reducing the compute resource usage in the BBU pool by 50% compared to baseline schemes.
During the last five decades, we have achieved significant milestones in our fight against TB with highly efficacious standardized antituberculous therapy provided through high-priority national ...health programs as a result of which there has been significant reduction in morbidity and case fatality rates across the world. According to a report by the WHO in 2010, an estimated 3.6% of (new) TB cases globally (total of 440,000) were MDR-TB. Above all, individual patients' experience through a 2-year long course of treatment with toxic drugs, i.e., adverse drug reaction (ADR), is the most important challenge that every physician struggles to tackle.
It is well known that the current ad hoc protocol suites do not scale to work efficiently in networks of more than a few hundred nodes. Most current ad hoc routing architectures use flat static ...addressing and thus, need to keep track of each node individually, creating a massive overhead problem as the network grows. Could dynamic addressing alleviate this problem? In this paper, we argue that the use of dynamic addressing can enable scalable routing in ad hoc networks. We provide an initial design of a routing layer based on dynamic addressing, and evaluate its performance. Each node has a unique permanent identifier and a transient routing address, which indicates its location in the network at any given time. The main challenge is dynamic address allocation in the face of node mobility. We propose mechanisms to implement dynamic addressing efficiently. Our initial evaluation suggests that dynamic addressing is a promising approach for achieving scalable routing in large ad hoc and mesh networks
In this paper, we report a subtle yet serious side channel vulnerability (CVE-2016-5696) introduced in a recent transmission control protocol (TCP) specification. The specification is faithfully ...implemented in Linux kernel version 3.6 (from 2012) and beyond, and affects a wide range of devices and hosts. In a nutshell, the vulnerability allows a blind off-path attacker to infer if any two arbitrary hosts on the Internet are communicating using a TCP connection. Further, if the connection is present, such an off-path attacker can also infer the TCP sequence numbers in use, from both sides of the connection; this in turn allows the attacker to cause connection termination and perform data injection attacks. We illustrate how the attack can be leveraged to disrupt or degrade the privacy guarantees of an anonymity network such as Tor, and perform web connection hijacking. Through extensive experiments, we show that the attack is fast and reliable. On average, it takes about 40 to 60 s to finish and the success rate is 88% to 97%. Finally, we propose changes to both the TCP specification and implementation to eliminate the root cause of the problem.
CPU memory prefetchers can substantially interfere with prime and probe cache side-channel attacks, especially on in-order CPUs which use aggressive prefetching. This interference is not accounted ...for in previous attacks. In this paper, we propose PAPP, a Prefetcher-Aware Prime Probe attack that can operate even in the presence of aggressive prefetchers. Specifically, we reverse engineer the prefetcher and replacement policy on several CPUs and use these insights to design a prime and probe attack that minimizes the impact of the prefetcher. We evaluate PAPP using Cache Side-channel Vulnerability (CSV) metric and demonstrate the substantial improvements in the quality of the channel under different conditions.
Adversarial attacks perturb images such that a deep neural network produces incorrect classification results. A promising approach to defend against adversarial attacks on natural multi-object scenes ...is to impose a context-consistency check, wherein, if the detected objects are not consistent with an appropriately defined context, then an attack is suspected. Stronger attacks are needed to fool such context-aware detectors. We present the first approach for generating context-consistent adversarial attacks that can evade the context-consistency check of black-box object detectors operating on complex, natural scenes. Unlike many black-box attacks that perform repeated attempts and open themselves to detection, we assume a "zero-query" setting, where the attacker has no knowledge of the classification decisions of the victim system. First, we derive multiple attack plans that assign incorrect labels to victim objects in a context-consistent manner. Then we design and use a novel data structure that we call the perturbation success probability matrix, which enables us to filter the attack plans and choose the one most likely to succeed. This final attack plan is implemented using a perturbation-bounded adversarial attack algorithm. We compare our zero-query attack against a few-query scheme that repeatedly checks if the victim system is fooled. We also compare against state-of-the-art context-agnostic attacks. Against a context-aware defense, the fooling rate of our zero-query approach is significantly higher than context-agnostic approaches and higher than that achievable with up to three rounds of the fewquery scheme.
Many MAC sub-layer protocols for supporting the usage of directional antennas in ad hoc networks have been proposed in literature. However, there remain two open issues that are yet to be resolved ...completely. First, in order to fully exploit the spatial diversity gains possible due to the use of directional antennas, it is essential to shift to the exclusive usage of directional antennas for the transmission and reception of all the MAC layer frames. This would facilitate maximal spatial reuse and will efface the phenomena of asymmetry in gain. Second, in the presence of mobility the MAC protocol should incorporate mechanisms by which a node can efficiently discover and track its neighbors. In this paper we propose PMAC, a new MAC protocol that addresses both the issues in an integrated way. PMAC incorporates an efficient mechanism for neighbor discovery, and a scheduling based medium sharing that allows for exclusive directional transmissions and receptions. We perform analysis and simulations to understand the performance of our scheme. We find that each node, on average, can achieve a per node utilization of about 80% in static and about 45% in mobile scenarios. In terms of throughput, our protocol is seen to outperform both the traditional IEEE 802.11 and previously proposed MAC protocols for use with directional antennas in ad hoc networks
PDF
