Denial of Service in Web-Domains: Building Defenses Against Next-Generation Attack Behavior

The existing state-of-the-art in the field of application layer Distributed Denial of Service (DDoS) protection is generally designed, and thus effective, only for static web domains. To the best of our knowledge, our work is the first that studies the problem of application layer DDoS defense in web domains of dynamic content and organization, and for next-generation bot behaviour. In the first part of this thesis, we focus on the following research tasks: 1) we identify the main weaknesses of the existing application-layer anti-DDoS solutions as proposed in research literature and in the industry, 2) we obtain a comprehensive picture of the current-day as well as the next-generation application-layer attack behaviour and 3) we propose novel techniques, based on a multidisciplinary approach that combines offline machine learning algorithms and statistical analysis, for detection of suspicious web visitors in static web domains. Then, in the second part of the thesis, we propose and evaluate a novel anti-DDoS system that detects a broad range of application-layer DDoS attacks, both in static and dynamic web domains, through the use of advanced techniques of data mining. The key advantage of our system relative to other systems that resort to the use of challenge-response tests (such as CAPTCHAs) in combating malicious bots is that our system minimizes the number of these tests that are presented to valid human visitors while succeeding in preventing most malicious attackers from accessing the web site. The results of the experimental evaluation of the proposed system demonstrate effective detection of current and future variants of application layer DDoS attacks

Assessment of Level-Of-Service for Freeway Segments Using HCM and Microsimulation Methods

AbstractThe Highway Capacity Manual (HCM) 2015 freeway facilities methodology offers a supplemental computational engine FREEVAL, which is a macroscopic/mesoscopic tool that enables users to implement HCM-based freeway analysis quickly and conveniently. On the other hand, Vissim is a microscopic simulation tool that enables users to model real-world conditions with high level of accuracy and comprehensiveness. Thus, the two tools represent quite opposite sides in freeway modelling – Vissim requires time-consuming preparation and calibration of the model but it usually provides benefits that are more comprehensive. FREEVAL requires less on input and calibration sides but its results may not be as beneficial as comprehensive and accurate as Vissim’s. The problem, that has not been addressed enough, is that we do not know how different their results are (when compared between themselves) and, at the same time, how close to the field conditions. Researchers and practitioners use both tools for freeway analysis and tend to compare the results directly. One of the commonly used performance measures is the Level of Service (LOS), which is used to quickly evaluate the freeway segment or facility performance. The HCM Freeway Facility Methodology uses density to estimate LOS. However, density is calculated differently in FREEVAL and Vissim, and comparing the estimated LOSs between the two may not represent a proper comparison. In essence, FREEVAL, in the under-saturated condition, estimates the density from the fundamental equations where the volume is estimated from the user entered demand and the speed is calculated using the statistical models provided in respective chapters of each segment type. On the other hand, Vissim tracks each individual vehicle as it moves along a freeway and calculates key performance measures by using individually modeled driver’s behavior. This paper aims to compare and contrast the methodologies behind the two tools and offer explanation and discussion of their outputs. The paper will cover four major HCM freeway segment types (basic, merge, diverge, and weaving) in under-saturated conditions. Field data will be acquired from a section of I-880 freeway in California. FREEVAL and Vissim models will be calibrated and validated using Mobile Century Data provided by University of California at Berkley and Caltrans Performance Measurement System. The output of both tools will be evaluated against the field data. The assessment should reveal the ability of each tool to replicate the real-world conditions. Paper results will contribute to the existing body of knowledge by filling the gap in the literature related to comparison and contrast of the key (LOS-related) performance measures of these two tools

Height and body-mass index trajectories of school-aged children and adolescents from 1985 to 2019 in 200 countries and territories: a pooled analysis of 2181 population-based studies with 65 million participants

Summary Background Comparable global data on health and nutrition of school-aged children and adolescents are scarce. We aimed to estimate age trajectories and time trends in mean height and mean body-mass index (BMI), which measures weight gain beyond what is expected from height gain, for school-aged children and adolescents. Methods For this pooled analysis, we used a database of cardiometabolic risk factors collated by the Non-Communicable Disease Risk Factor Collaboration. We applied a Bayesian hierarchical model to estimate trends from 1985 to 2019 in mean height and mean BMI in 1-year age groups for ages 5–19 years. The model allowed for non-linear changes over time in mean height and mean BMI and for non-linear changes with age of children and adolescents, including periods of rapid growth during adolescence. Findings We pooled data from 2181 population-based studies, with measurements of height and weight in 65 million participants in 200 countries and territories. In 2019, we estimated a difference of 20 cm or higher in mean height of 19-year-old adolescents between countries with the tallest populations (the Netherlands, Montenegro, Estonia, and Bosnia and Herzegovina for boys; and the Netherlands, Montenegro, Denmark, and Iceland for girls) and those with the shortest populations (Timor-Leste, Laos, Solomon Islands, and Papua New Guinea for boys; and Guatemala, Bangladesh, Nepal, and Timor-Leste for girls). In the same year, the difference between the highest mean BMI (in Pacific island countries, Kuwait, Bahrain, The Bahamas, Chile, the USA, and New Zealand for both boys and girls and in South Africa for girls) and lowest mean BMI (in India, Bangladesh, Timor-Leste, Ethiopia, and Chad for boys and girls; and in Japan and Romania for girls) was approximately 9–10 kg/m2. In some countries, children aged 5 years started with healthier height or BMI than the global median and, in some cases, as healthy as the best performing countries, but they became progressively less healthy compared with their comparators as they grew older by not growing as tall (eg, boys in Austria and Barbados, and girls in Belgium and Puerto Rico) or gaining too much weight for their height (eg, girls and boys in Kuwait, Bahrain, Fiji, Jamaica, and Mexico; and girls in South Africa and New Zealand). In other countries, growing children overtook the height of their comparators (eg, Latvia, Czech Republic, Morocco, and Iran) or curbed their weight gain (eg, Italy, France, and Croatia) in late childhood and adolescence. When changes in both height and BMI were considered, girls in South Korea, Vietnam, Saudi Arabia, Turkey, and some central Asian countries (eg, Armenia and Azerbaijan), and boys in central and western Europe (eg, Portugal, Denmark, Poland, and Montenegro) had the healthiest changes in anthropometric status over the past 3·5 decades because, compared with children and adolescents in other countries, they had a much larger gain in height than they did in BMI. The unhealthiest changes—gaining too little height, too much weight for their height compared with children in other countries, or both—occurred in many countries in sub-Saharan Africa, New Zealand, and the USA for boys and girls; in Malaysia and some Pacific island nations for boys; and in Mexico for girls. Interpretation The height and BMI trajectories over age and time of school-aged children and adolescents are highly variable across countries, which indicates heterogeneous nutritional quality and lifelong health advantages and risks

Unsupervised Clustering of Web Sessions to Detect Malicious and Non-malicious Website Users

AbstractDenial of Service (DoS) attacks are recognized as one of the most damaging attacks on the Internet security today. Recently, malicious web crawlers have been used to execute automated DoS attacks on web sites across the WWW. In this study, we examine the use of two unsupervised neural network (NN) learning algorithms for the purpose web-log analysis: the Self- Organizing Map (SOM) and Modified Adaptive Resonance Theory 2 (Modified ART2). In particular, through the use of SOM and Modified ART2, our work aims to obtain a better insight into the types and distribution of visitors to a public web-site based on their link-traversal behaviour, as well as to investigate the relative differences and/or similarities between malicious web crawlers and other non-malicious visitor groups. The results of our study show that, even though there is a pretty clear separation between malicious web-crawlers and other visitor groups, around 8% of malicious crawlers exhibit very ‘human-like’ browsing behaviour and as such pose a particular challenge for future web-site security systems

Carbon Supported PtSn versus PtSnO2 Catalysts in Methanol Oxidation

Pt, PtSn and PtSnO2 catalysts supported on high surface area carbon synthesized by microwave assisted polyol procedure were tested for methanol oxidation. Based on TGA, EDX and XRD analysis, PtSn/C is composed of Pt and Pt3Sn phase while the rest of Sn is present in a form of very small tin oxide particles. This paper focuses on structure-activity relationships for CO tolerance and methanol oxidation reactions after addition of Sn to Pt catalysts. Alloying of Sn with Pt improves the rate of CO oxidation despite the fact that the pure Sn does not react with CO and therefore activity for methanol oxidation increases similar to 2 times in comparison to Pt/C catalyst. PtSn/C catalyst shows small advantage in comparison with PtSnO2/C catalyst due to the alloyed Sn and its electronic effect. Long term stability tests also confirmed that PtSn/C catalyst is somewhat better in comparison to PtSnO2/C

High dose of ethanol decreases total spectral power density in seizures induced by D,L-homocysteine thiolactone in adult rats

The effects of ethanol on epilepsy are very complex. Ethanol can have depressant as well as excitatory effect on different animal models of epilepsy. Systemic administration of homocysteine can trigger seizures. The aim of the present study was to examine the changes of total spectral power density after ethanol alone and together with homocysteine thiolactone in adult rats. Adult male Wistar rats were divided into following groups: I. saline-injected, (control) C; 2. D, L-homocysteine thiolactone, H (8 mmol/kg); 3. ethanol, E (E(0.5), 0.5 g/kg; E(1), 1 g/kg; E(2), 2 g/kg) and 4. E (E(0.5), E(1), and E(2)) 30 min prior to H, EH (E(0.5)H, E(1)H and E(2)H). For EEG recordings three gold-plated screws were implanted into the skull. Our results demonstrate that ethanol, when applied alone, increased total EEG spectral power density of adult rats with a marked spectrum shift toward low frequency waves. In EH groups, increasing doses of ethanol exhibited a dose-dependent effect upon spectral power density. Ethanol increased EEG spectral power density in E(0.5)H and E(1)H group, comparing to the H group (p GT 0.05), the maximal increase was recorded with the lowest ethanol dose applied. The highest dose of ethanol (E(2)H) significantly decreased total power spectra density, comparing to the H group. We can conclude that high doses of ethanol depressed marked increase in EEG power spectrum induced by D,L-homocysteine thiolactone

Synthesis and Characterization of 3-(1-((3,4-Dihydroxyphenethyl)amino)ethylidene)-chroman-2,4-dione as a Potential Antitumor Agent

© 2019 Dušan S. Dimić et al. The newly synthesized coumarin derivative with dopamine, 3-(1-((3,4-dihydroxyphenethyl)amino)ethylidene)-chroman-2,4-dione, was completely structurally characterized by X-ray crystallography. It was shown that several types of hydrogen bonds are present, which additionally stabilize the structure. The compound was tested in vitro against different cell lines, healthy human keratinocyte HaCaT, cervical squamous cell carcinoma SiHa, breast carcinoma MCF7, and hepatocellular carcinoma HepG2. Compared to control, the new derivate showed a stronger effect on both healthy and carcinoma cell lines, with the most prominent effect on the breast carcinoma MCF7 cell line. The molecular docking study, obtained for ten different conformations of the new compound, showed its inhibitory nature against CDK S protein. Lower inhibition constant, relative to one of 4-OH-coumarine, proved stronger and more numerous interactions with CDK S protein. These interactions were carefully examined for both parent molecule and derivative and explained from a structural point of view

Immunomodulatory actions of central ghrelin in diet-induced energy imbalance

We investigated the effects of centrally administered orexigenic hormone ghrelin on energy imbalance-induced inflammation. Rats were subjected for four weeks to three different dietary regimes: normal (standard food), high-fat (standard food with 30% lard) or food-restricted (70%, 50%, 40% and 40% of the expected food intake in 1st, 2nd, 3rd and 4th week, respectively). Compared to normal-weight controls, starved, but not obese rats had significantly higher levels of proinflammatory cytokines (TNF, IL-1 beta, IFN-gamma) in the blood. When compared to normally fed animals, the hearts of starved and obese animals expressed higher levels of mRNAs encoding proinflammatory mediators (TNF, IL-1 beta, IL-6, IFN-gamma, IL-17, IL-12, iNOS), while mRNA levels of the anti-inflammatory TGF-beta remained unchanged. Intracerebroventricular (ICV) injection of ghrelin (1 mu g/day) for five consecutive days significantly reduced TNF, IL-1 beta and IFN-gamma levels in the blood of starved rats, as well as TNF, IL-17 and IL-12p40 mRNA expression in the hearts of obese rats. Conversely, ICV ghrelin increased the levels of 1FN-gamma, IL-17,1L-12p35 and IL-12p40 mRNA in the heart tissue of food-restricted animals. This was associated with an increase of immunosuppressive ACTH/corticosterone production in starved animals and a decrease of the immunostimulatory adipokine leptin both in food-restricted and high-fat groups. Ghrelin activated the energy sensor AMP-activated protein kinase (AMPK) in the hypothalamus and inhibited extracellular signal-regulated kinase (ERK) in the hearts of obese, but not starved rats. Therefore, central ghrelin may play a complex role in energy imbalance-induced inflammation by modulating HPA axis, leptin and AMPK/ERK signaling pathways. (C) 2011 Elsevier Inc. All rights reserved