948 resultados para flash crowd attack


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DeAuthentication Denial of Service attacks in Public Access WiFi operate by exploiting the lack of authentication of management frames in the 802.11 protocol. Detection of these attacks rely almost exclusively on the selection of appropriate thresholds. In this work the authors demonstrate that there are additional, previously unconsidered, metrics which also influence DoS detection performance. A method of systematically tuning these metrics to optimal values is proposed which ensures that parameter choices are repeatable and verifiable.

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We consider the problem of self-healing in peer-to-peer networks that are under repeated attack by an omniscient adversary. We assume that, over a sequence of rounds, an adversary either inserts a node with arbitrary connections or deletes an arbitrary node from the network. The network responds to each such change by quick “repairs,” which consist of adding or deleting a small number of edges. These repairs essentially preserve closeness of nodes after adversarial deletions, without increasing node degrees by too much, in the following sense. At any point in the algorithm, nodes v and w whose distance would have been l in the graph formed by considering only the adversarial insertions (not the adversarial deletions), will be at distance at most l log n in the actual graph, where n is the total number of vertices seen so far. Similarly, at any point, a node v whose degree would have been d in the graph with adversarial insertions only, will have degree at most 3d in the actual graph. Our distributed data structure, which we call the Forgiving Graph, has low latency and bandwidth requirements. The Forgiving Graph improves on the Forgiving Tree distributed data structure from Hayes et al. (2008) in the following ways: 1) it ensures low stretch over all pairs of nodes, while the Forgiving Tree only ensures low diameter increase; 2) it handles both node insertions and deletions, while the Forgiving Tree only handles deletions; 3) it requires only a very simple and minimal initialization phase, while the Forgiving Tree initially requires construction of a spanning tree of the network.

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The increased complexity and interconnectivity of Supervisory Control and Data Acquisition (SCADA) systems in the Smart Grid has exposed them to a wide range of cyber-security issues, and there are a multitude of potential access points for cyber attackers. This paper presents a SCADA-specific cyber-security test-bed which contains SCADA software and communication infrastructure. This test-bed is used to investigate an Address Resolution Protocol (ARP) spoofing based man-in-the-middle attack. Finally, the paper proposes a future work plan which focuses on applying intrusion detection and prevention technology to address cyber-security issues in SCADA systems.

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We consider the problem of self-healing in peer-to-peer networks that are under repeated attack by an omniscient adversary. We assume that, over a sequence of rounds, an adversary either inserts a node with arbitrary connections or deletes an arbitrary node from the network. The network responds to each such change by quick "repairs," which consist of adding or deleting a small number of edges. These repairs essentially preserve closeness of nodes after adversarial deletions,without increasing node degrees by too much, in the following sense. At any point in the algorithm, nodes v and w whose distance would have been - in the graph formed by considering only the adversarial insertions (not the adversarial deletions), will be at distance at most - log n in the actual graph, where n is the total number of vertices seen so far. Similarly, at any point, a node v whose degreewould have been d in the graph with adversarial insertions only, will have degree at most 3d in the actual graph. Our distributed data structure, which we call the Forgiving Graph, has low latency and bandwidth requirements. The Forgiving Graph improves on the Forgiving Tree distributed data structure from Hayes et al. (2008) in the following ways: 1) it ensures low stretch over all pairs of nodes, while the Forgiving Tree only ensures low diameter increase; 2) it handles both node insertions and deletions, while the Forgiving Tree only handles deletions; 3) it requires only a very simple and minimal initialization phase, while the Forgiving Tree initially requires construction of a spanning tree of the network. © Springer-Verlag 2012.

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Rural communities in the Haut-Uele Province of northern Democratic Republic of Congo live in constant danger of attack and/or abduction by units of the Lord's Resistance Army operating in the region. This pilot study sought to develop and evaluate a community-participative psychosocial intervention involving life skills and relaxation training and Mobile Cinema screenings with this war-affected population living under current threat. 159 war-affected children and young people (aged 7-18) from the villages of Kiliwa and Li-May in north-eastern DR Congo took part in this study. In total, 22% of participants had been abduction previously while 73% had a family member abducted. Symptoms of post-traumatic stress reactions, internalising problems, conduct problems and pro-social behaviour were assessed by blinded interviewers at pre- and post-intervention and at 3-month follow-up. Participants were randomised (with an accompanying caregiver) to 8 sessions of a group-based, community-participative, psychosocial intervention (n=79) carried out by supervised local, lay facilitators or a wait-list control group (n=80). Average seminar attendance rates were high: 88% for participants and 84% for caregivers. Drop-out was low: 97% of participants were assessed at post-intervention and 88% at 3 month follow-up. At post-test, participants reported significantly fewer symptoms of post-traumatic stress reactions compared to controls (Cohen's d=0.40). At 3 month follow up, large improvements in internalising symptoms and moderate improvements in pro-social scores were reported, with caregivers noting a moderate to large decline in conduct problems among the young people. Trial Registration clinicalTrials.gov, Identifier: NCT01542398.

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In this short paper, we present an integrated approach to detecting and mitigating cyber-attacks to modern interconnected industrial control systems. One of the primary goals of this approach is that it is cost effective, and thus whenever possible it builds on open-source security technologies and open standards, which are complemented with novel security solutions that address the specific challenges of securing critical infrastructures.

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In this work, a laser-produced plasma extreme ultraviolet source and a free electron laser were used to create Ne photo-ionized plasmas. In both cases, a radiation beam was focused onto a gas stream injected into a vacuum chamber synchronously with the radiation pulse. Extreme ultraviolet radiation from the plasma spanned a wide spectral range with pronounced maximum centered at lambda = 11 +/- 1 nm while the free electron laser pulses were emitted at a wavelength of 32 nm. The power density of the focused plasma radiation was approximately 2 x 10(7) W/cm(2) and was seven orders of magnitude lower compared with the focused free electron laser beam. Radiation fluences in both experimental conditions were comparable. Despite quite different spectral characteristics and extremely different power densities, emission spectra of both photo-ionized plasmas consist of the same spectral lines within a wavelength range of 20 to 50 nm, however, with different relative intensities of the corresponding lines. The dominating spectral lines originated from singly charged ions (Ne II); however, Ne III lines were also detected. Additionally, computer simulations of the emission spectra, obtained for photo-ionized plasmas, driven by the plasma extreme ultraviolet source, were performed. The corresponding measured and calculated spectra are presented. An electron temperature and ionic composition were estimated. Differences between the experimental spectra, obtained for both irradiation conditions, were analyzed. The differences were attributed mainly to different energies of driving photons.

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We report on experiments aimed at the generation and characterization of solid density plasmas at the free-electron laser FLASH in Hamburg. Aluminum samples were irradiated with XUV pulses at 13.5 nm wavelength (92 eV photon energy). The pulses with duration of a few tens of femtoseconds and pulse energy up to 100 mu J are focused to intensities ranging from 10(13) to 10(17) W/cm(2). We investigate the absorption and temporal evolution of the sample under irradiation by use of XUV spectroscopy. We discuss the origin of saturable absorption, radiative decay, bremsstrahlung and ionic line emission. Our experimental results are in good agreement with hydrodynamic simulations.

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A new niche of densely populated, unprotected networks is becoming more prevalent in public areas such as Shopping Malls, defined here as independent open-access networks, which have attributes that make attack detection more challenging than in typical enterprise networks. To address these challenges, new detection systems which do not rely on knowledge of internal device state are investigated here. This paper shows that this lack of state information requires an additional metric (The exchange timeout window) for detection of WLAN Denial of Service Probe Flood attacks. Variability in this metric has a significant influence on the ability of a detection system to reliably detect the presence of attacks. A parameter selection method is proposed which is shown to provide reliability and repeatability in attack detection in WLANs. Results obtained from ongoing live trials are presented that demonstrate the importance of accurately estimating probe request and probe response timeouts in future Independent Intrusion Detection Systems.

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A novel electrical current applied technique known as flash sintering has been applied to rapidly (within 10 min) densify electrolytes including Ce0.8Gd0.2O1.9 (GDC20), Ce0.9Gd0.1O1.95 (GDC10), and Ce0.8Sm0.2O1.9 (SDC20) for application in Solid Oxide Fuel Cells (SOFCs). The densification temperature for the three electrolytes was 554°C, 635°C, and 667°C, respectively, which is far below conventional sintering temperatures. All specimens after flash sintering maintained the pure fluorite structure and exhibited a well-densified microstructure. To investigate the flash-sintering mechanism, we have applied Joule heating effect with blackbody radiation theory, and found that this theory could reasonably interpret the flash-sintering phenomenon by matching theoretically calculated temperature with the real temperature. More importantly, one of the materials inherent properties, the electronic conductivity, has been found correlated with the onset of flash sintering, which indicates that the electrons and holes are the primary current carriers during the start of flash-sintering process. As a result, potential densification mechanisms have been discussed in terms of spark plasma discharge.

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The alkali activation of waste products has become a widespread topic of research, mainly due to environmental benefits. Portland cement and alkali-activated mortar samples were prepared to compare their resistance to silage effluent which contains lactic acid. The mechanism of attack on each sample has also been investigated.

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Masked implementations of cryptographic algorithms are often used in commercial embedded cryptographic devices to increase their resistance to side channel attacks. In this work we show how neural networks can be used to both identify the mask value, and to subsequently identify the secret key value with a single attack trace with high probability. We propose the use of a pre-processing step using principal component analysis (PCA) to significantly increase the success of the attack. We have developed a classifier that can correctly identify the mask for each trace, hence removing the security provided by that mask and reducing the attack to being equivalent to an attack against an unprotected implementation. The attack is performed on the freely available differential power analysis (DPA) contest data set to allow our work to be easily reproducible. We show that neural networks allow for a robust and efficient classification in the context of side-channel attacks.