45 research outputs found

    On modeling and mitigating new breed of dos attacks

    Get PDF
    Denial of Service (DoS) attacks pose serious threats to the Internet, exerting in tremendous impact on our daily lives that are heavily dependent on the good health of the Internet. This dissertation aims to achieve two objectives:1) to model new possibilities of the low rate DoS attacks; 2) to develop effective mitigation mechanisms to counter the threat from low rate DoS attacks. A new stealthy DDoS attack model referred to as the quiet attack is proposed in this dissertation. The attack traffic consists of TCP traffic only. Widely used botnets in today\u27s various attacks and newly introduced network feedback control are integral part of the quiet attack model. The quiet attack shows that short-lived TCP flows used as attack flows can be intentionally misused. This dissertation proposes another attack model referred to as the perfect storm which uses a combination of UDP and TCP. Better CAPTCHAs are highlighted as current defense against botnets to mitigate the quiet attack and the perfect storm. A novel time domain technique is proposed that relies on the time difference between subsequent packets of each flow to detect periodicity of the low rate DoS attack flow. An attacker can easily use different IP address spoofing techniques or botnets to launch a low rate DoS attack and fool the detection system. To mitigate such a threat, this dissertation proposes a second detection algorithm that detects the sudden increase in the traffic load of all the expired flows within a short period. In a network rate DoS attacks, it is shown that the traffic load of all the expired flows is less than certain thresholds, which are derived from real Internet traffic analysis. A novel filtering scheme is proposed to drop the low rate DoS attack packets. The simulation results confirm attack mitigation by using proposed technique. Future research directions will be briefly discussed

    Defense techniques for low-rate DoS attacks against application servers

    Get PDF
    a b s t r a c t Low-rate denial of service (DoS) attacks have recently emerged as new strategies for denying networking services. Such attacks are capable of discovering vulnerabilities in protocols or applications behavior to carry out a DoS with low-rate traffic. In this paper, we focus on a specific attack: the low-rate DoS attack against application servers, and address the task of finding an effective defense against this attack. Different approaches are explored and four alternatives to defeat these attacks are suggested. The techniques proposed are based on modifying the way in which an application server accepts incoming requests. They focus on protective measures aimed at (i) preventing an attacker from capturing all the positions in the incoming queues of applications, and (ii) randomizing the server operation to eliminate possible vulnerabilities due to predictable behaviors. We extensively describe the suggested techniques, discussing the benefits and drawbacks for each under two criteria: the attack efficiency reduction obtained, and the impact on the normal operation of the server. We evaluate the proposed solutions in a both a simulated and a real environment, and provide guidelines for their implementation in a production system

    Knowledge acquisition for autonomic network management in emerging self-organizing architectures

    Get PDF
    Tesis inédita de la Universidad Complutense de Madrid, Facultad de Informática, Departamento de Ingeniería del Software e Inteligencia Artificial, leída el 19/12/2018Los escenarios de red emergentes estan caracterizados por el acceso intensivo a una amplia gama de servicios y aplicaciones que han incrementado las exigencias de las redes de comunicacion. Los modelos de gestion de red tradicionales se han caracterizado a su vez por una alta dependencia del factor humano para llevar a cabo tareas de configuracion y mantenimiento de la red. Esta situacion se ha hecho menos sostenible en las redes moviles no solo por los costes operacionales y de inversion de capital asociados, sino tambien por la complejidad que estas han adquirido ante la inmersion exponencial de dispositivos moviles. Tales aspectos han motivado el surgimiento de la quinta generacion de redes moviles, caracterizadas por indicadores de desempeño ambiciosos que deben cumplirse para satisfacer los niveles de servicio acordados...Emerging network scenarios are characterized by intensive access to a wide range of services and applications that have increased the demands of communication networks. The traditional network management models have been characterized by a high dependence on the human factor to carry out network configuration and maintenance tasks. This situation has become less sustainable in mobile networks not only due to the associated operational (COPEX) and capital investment costs (CAPEX), but also due to the complexity they have acquired when facing the exponential immersion of mobile devices. These aspects have led to the emergence of the fifth generation of mobile networks, characterized by ambitious performance indicators that must be fulfilled to meet the agreed service levels...Fac. de InformáticaTRUEunpu

    Report from the 1st MYCOKEY international conference Global Mycotoxin Reduction in the Food and Feed Chain held in Ghent, Belgium, 11-14 September 2017

    Get PDF
    Aflatoxins are cancer-promoting natural toxins that are produced by the fungus Aspergillus flavus and Aspergillus parasiticus. Aflatoxins have been regarded as one of the most fatal threat in food safety, due to their strong hepatotoxic, carcinogenic and teratogenic effects on human beings and animals. Among them, aflatoxin B1 (AFB1) is one of the common types which have received considerable attention. Thus, developing a rapid, simple and reliable method for determination of AFB1 in foods is very important. Herein, a preliminary study of Frster resonance energy transfer (FRET) immunoassay based on the cadmium-free quantum dots for determination of AFB1 was described. To avoid the use of hazardous heavy metals, core/shell InP/ZnS quantum dots (QDs) as an alternative for Cd-based QDs were synthesized. A silica shell with epoxy groups was used for water solubilization of the obtained nanoparticles. Then a specific anti-AFB1 monoclonal antibody (mAb) was labelled with the hydrophilic QDs via these highly reactive epoxy groups. Gel electrophoresis was used to control the binding. After that, the FRET system was developed using the Cd-free QDs conjugate as donor. Graphene oxide was selected as acceptor. In order to keep the distance between donor and acceptor close enough, the size of silica coated QDs should be controlled strictly. We found that 1-dodecantiol which was used for ligands change on the surface of InP/ZnS QDs was better than oleylamine and the optimum amount of tetraoxysilane was 5 mu L in the silylanization. Besides, only ethanol and hexane were used to wash silica coated QDs which could ensure good dispersion of QDs in water. The cut-off value for the determination of AFB1 in tube was 10 ng/mL with a preliminary study. Compared to reported FRET assays with Cd-based QDs, the developed FRET was easy-to-operate, visual and safe

    The Nature and Experience of Anxiety in Bipolar Disorder.

    Get PDF
    Anxiety experiences (defined either categorically as a disorder or on continua as symptoms) have been found to be highly prevalent in bipolar disorder (BD) and have been consistently associated with poorer outcomes. Current research in this area has primarily focused on prevalence rates of anxiety disorders and their association to retrospective outcomes. There is a lack of research regarding the psychological processes which may underlie the relationship between anxiety and bipolar mood experiences and current psychological models of BD have generally omitted anxiety in their explanations of mood swings. A qualitative meta-synthesis and semi-structured interviews were employed in this thesis to explore the lived experience of anxiety in BD. A longitudinal analysis of data from a large scale RCT was also conducted to assess a range of categorical and continuous measures of anxiety as predictors of outcome in BD. Finally, experience sampling methodology assessed momentary interactions between anxiety and affect in daily life for individuals with BD and non-clinical controls. Anxiety was found to be intrinsically linked to bipolar mood experiences across methodologies. Subjectively, anxiety was perceived as a trigger to both depressed and manic experiences. Anxiety about relapse due to extreme negative appraisals of mood swings was reported and impacted on several important life domains including quality of life, sleep, relationships and employment. Anxiety was consistently associated with increased depression and reduced functioning across all studies. Anxiety and mania were found to have both positive and negative associations across studies. The continuous measurement of anxiety, rather than categorical, was the most reliable predictor of outcome longitudinally when carefully controlling for a range of extraneous variables. The results provide support for anxiety as an intrinsic experience in BD and encourage the consideration of integrated psychological models and treatment approaches which include anxiety as a core feature of BD

    The negotiation of belonging: An exploration of the roles of kinship and the state among elderly West Indian migrants residing in a sheltered housing scheme in Brixton, London.

    Get PDF
    This thesis is concerned with the contemporary experiences of long-term West Indian migrants to Britain, residing in a sheltered housing scheme in Brixton. It assesses their multi-layered negotiation of belonging, connections with the West Indies, their family and the British nation state amid the issues of race and social exclusion. The elderly people in this research migrated to improve their economic and social status. However, due to combined factors, such as estrangement from home and fragmented familial structures that do not fully support them, they maintained their original working-class status. They rely on state services but tensions in service provision test their inclusion. The housing scheme aims to create a community where the elderly people can associate with each other, bond, locate and root in the scheme and in the external local community. However, factions and divisions arise affecting their belonging. In addition, gender differentiation became apparent as my male informants are less connected to their family. Overall, my elderly informants remained culturally aligned to their sense of remaining West Indian despite the multiplicity of 'disjunctures' (Appadurai 1996, Besson 2005) they encounter amid shifting and fluid boundaries. Indeed, many travel to and from the West Indies. However, as the unsuccessful returnees show they cannot permanently settle due to kinship estrangement, insufficient finance and reliance on the British state. Therefore, I suggest, they stayed in England by default, becoming 'marginal within places'. Utilising Gramsci's (1990) approach to social change I assess my informants' agency and the agency of others on their behalf as the migrants strive to maintain their identity, culture and place within complex contemporary society. Bhabha's (1994) concepts of 'hybridity' and the 'third space' contribute to my analysis, highlighting the contradictory and confusing issues associated with the migrants' culture of movement, challenging the notions of settlement, inclusion and belonging
    corecore