Les travaux réalisés dans cette thèse se situent dans le domaine des réseaux de capteurs sans fil (Wireless Sensor Networks), déployés en environnement urbain et se focalisent sur la sécurité des protocoles de routage multi-sauts. Les capteurs sont souvent déployés dans des environnements ouverts et accessibles permettant aux éventuels attaquants de les détruire ou de les capturer afin d'en extraire les données sensibles (clés de chiffrement, identité, adresse, etc.). Les méthodes traditionnelles, basées sur la cryptographie, permettent d'obtenir une sécurité de base (authentification, confidentialité, intégrité, non répudiation etc.), mais ne permettent pas toujours de se prémunir contre les attaques dues à la compromission des nœuds (réplication des nœuds, Sybil, Selective forwarding, Blackhole, Sinkhole, Wormhole etc.). Dans le but d'apporter des solutions algorithmiques complémentaires aux solutions cryptographiques, nous étudions la résilience des protocoles de communication en présence d'adversaires internes visant à perturber l'acheminement de l'information à travers le réseau. Dans un premier temps, nous introduisons la notion de résilience et une métrique quantitative doublée d'une représentation qualitative pour mieux l'appréhender. Nous étudions les principaux protocoles de routage de la littérature selon notre métrique pour montrer leur capacité d'être résilients. Cette étude nous permet de proposer trois mécanismes visant à développer la résilience: (i) l'introduction de comportements aléatoires, (ii) la limitation de la longueur des routes et (iii) la réplication de paquets. Nous appliquons ces mécanismes aux protocoles classiques et nous les étudions selon notre métrique. Pour confirmer les résultats de simulations, nous proposons enfin un travail théorique pour mesurer analytiquement la résilience en nous basant sur le modèle des marches aléatoires biaisées. / This thesis focuses on the security issues of multi-hop routing protocols for Wireless Sensor Networks (WSNs). The rapid deployment capabilities, due to the lack of infrastructure, as well as the self organized and potentially fault-tolerant nature of WSNs make them attractive for multiple applications spanning from environmental monitoring (temperature, pollution, etc.) to building industrial automation (electricity/gas/water metering, event detection, home automation etc). Security is particularly challenging in WSNs. Because of their open and unattended deployment, in possibly hostile environments, powerful adversaries can easily launch Denial-of-Service (Dos) attacks, cause physical damage to sensors, or even capture them to extract sensitive information (encryption keys, identities, addresses etc.). After node compromise, an adversary can seek to disrupt the functionality of network layer by launching attacks such as node replication, Sybil, Selective forwarding, Sinkhole, Wormhole etc. To cope with these "insider" attacks, stemming from node compromise, "beyond cryptography" algorithmic solutions must be envisaged to complement the traditional cryptographic solutions. Firstly, we propose the resiliency concept including our definition and a new metric to compare routing protocols. This method allows to aggregate meaningfully several parameters (quantitative information) and makes it easier to visually discern various tradeoffs (qualitative information), thus greatly simplifying the process of protocol comparison. Secondly, we propose the protocol behaviors enhancing resiliency. Our proposition consists in three strategies: (i) introduce random behaviors (ii) limit route length (iii) introduce data replication. These mechanisms are applied to several well known routing protocols to study their resiliency. Finally, a theoretical study of resiliency is introduced. We present an analytical study of biased random walks under attacks to confirm the results obtained through simulations.

A Internet tem se tornado uma plataforma importante para interação e compartilhamento de arquivos, o que motivou uma crescente demanda por serviços eficientes. Sistemas de distribuição de conteúdo (CDS) precisaram ser criados visando modernidade e robustez. No contexto desta tese, CDS são definidos como sistemas usados para compartilhar qualquer tipo de conteúdo na Internet. Duas categorias de CDS se destacam como as mais populares: compartilhamento de arquivos e sistemas de mídia contínua. Arquiteturas par-a-par (P2P) surgiram como potenciais soluções para o aprimoramento da disseminação de conteúdo nos CDS. Nesse contexto, a popularização das arquiteturas P2P motivou a comunidade científica a investigar alguns aspectos de pesquisa desafiadores, e.g., otimização de topologias de redes, mecanismos de inicialização de sistemas e serviços de descoberta de recursos. Um desafio com interesse especial a esta tese diz respeito a mecanismos para conciliar a preferência dos usuários aos conteúdos publicados. Esse aspecto é importante para garantir uma boa qualidade de experiência (QoE) aos usuários dos sistemas, uma vez que podem existir divergências entre opiniões na descrição dos conteúdos e ações maliciosas. Esforços de pesquisa constantes têm sido feitos para combater poluição de conteúdo em CDS. Abordagens buscam construir uma base de conhecimento sobre poluidores e conteúdos poluídos para identificar e isolar conteúdos suspeitos depois que eles são publicados. Entretanto, o tempo de reação dessas abordagens até considerar um conteúdo poluído é consideravelmente longo, permitindo uma ampla disseminação de poluição. Além disso, algumas abordagens anteriores buscam polarizar conteúdos entre poluídos ou não, desconsiderando a intrínseca subjetividade acerca da classificação dos conteúdos compartilhados. O objetivo principal desta tese é propor um mecanismo para prover uma boa QoE aos usuários – agindo proativamente durante as fases iniciais da publicação dos conteúdos – e reduzir os efeitos de interferências maliciosas. Para alcançar tal objetivo, três passos principais guiaram o trabalho de pesquisa apresentado nesta tese. Primeiro, propusemos uma estratégia inovadora que opera de forma conservadora para conter a disseminação de poluição. Segundo, estendemos nossa solução para lidar com a subjetividade acerca das descrições dos conteúdos. Terceiro, tratamos o ataque de poluição como um ataque massivo. Para avaliar a solução, experimentos foram executados utilizando testes reais e simulações. Resultados ressaltaram a importância de adotar medidas de segurança para combater comportamentosmaliciosos em CDS. Na ausência de mecanismos de contramedida, pequenas proporções (10%) de atacantes foram capazes de comprometer o sistema. A instanciação da estratégia conservadora proposta nesta tese demonstrou a eficácia em atrasar usuários para contornar ataques massivos. / The Internet has become a large platform where users can interact and share personal files or third-party productions. Considering the increasing demand for efficient content sharing, modern and robust content distribution systems (CDS) need to be deployed and maintained. In the context of this thesis, CDS are defined as systems used for sharing any kind of content on the Internet. Two categories of CDS are underscored as the most popular ones: file sharing and streaming systems. Peer-to-peer (P2P) architectures have emerged as a potential solution to improve content dissemination in CDS. The popularization of P2P architectures, in the context of CDS,motivated the scientific community to investigate some challenging problems, namely network topology optimization, bootstrap mechanisms, and service discovery. One particular interesting challenge, in the context of this thesis, is related to mechanisms to approximate users to their personal interests. This is important to guarantee good quality of experience (QoE) to users when searching for content. Imprecise descriptions are likely to happen due to different users’ opinion or malicious behavior. Substantial research has been carried out to fight content pollution in CDS. Proposed approaches try to identify and isolate suspicious content after publication. The rationale is to build a base of knowledge about polluters and fake content. However, the reaction time until a content is considered polluted is considerably long, which allows pollution to get widely disseminated. Furthermore, some previous approaches attempt to polarize contents in either polluted or not, not taking into account the inherent subjectivity behind the evaluation of shared contents. The main objective of this thesis is to devise a mechanism to provide users a good QoE – by acting proactively in the early stages of content distribution life cycle – and reduce the effect of malicious interferences. To achieve that, three main steps guided the research work presented in this thesis. First, we proposed a novel strategy that operates conservatively to avoid wide pollution dissemination. Second, we extended our previous solution to cope with the subjectivity regarding content descriptions. Third, and last, we address the pollution attack as a massive attack. To evaluate our solution, a set of experiments was carried out using both real tests and simulations. Results showed the importance of adopting security measures to mitigate malicious behavior in CDS. In the absence of countermeasure mechanisms, even a small proportion (10%) of attackers was able to subvert the system. The introduction of a conservative strategy in this thesis demonstrated the efficacy of delaying users in circumventing massive attacks.

The subject of web server security is vast, and it is becoming bigger as time passes by. Every year, researches, both private and public, are adding to the number of possible threats to the security of web servers, and coming up with possible solutions to them. A number of these solutions are considered to be expensive, complex, and incredibly time-consuming, while not able to create the perfect web to challenge any breach to the server security. In the study that follows, an attempt will be made to check whether a particular firewall can ensure a strong security measure and deal with some security breaches or severe threat to an existing web server. The research conducted has been done with the CSF Firewall, which provides a suit of scripts that ensure a portal’s security through a number of channels. The experiments conducted under the research provided extremely valuable insights about the application in hand, and the number of ways the CSF Firewall can help in safety of a portal against Secured Shell (SSH) attacks, dedicated to break the security of it, in its initial stages. It further goes to show how simple it is to actually detect the prospective attacks, and subsequently stop the Denial of Service (DoS) attacks, as well as the port scans made to the server, with the intent of breaching the security, by finding out an open port. By blocking the IP Addresses of the attackers dedicated to such an act, preventing them from creating nuisance, the CSF Firewall has been able to keep alien intrusions away from the server. It also aids in creating a secure zone for the server, to continue smoothly, while alerting the server administrators of the same, and gives them an opportunity to check those threatening IPs, and the time of attack, makes sure that the server administrators stay alert in the future, and is able to keep an eye on such attacks. In doing this, the experiment adds valuable data in the effective nature of the CSF Firewall.

Le cloud computing, solution souple et peu couteuse, est aujourd'hui largement adopté pour la production à grande échelle de services IT. Toutefois, des utilisateurs malveillants tirent parti de ces caractéristiques pour bénéficier d'une plate-forme d'attaque prête à l'emploi dotée d'une puissance colossale. Parmi les plus grands bénéficiaires de cette conversion en vecteur d’attaque, les botclouds sont utilisés pour perpétrer des attaques de déni de service distribuées (DDoS) envers tout tiers connecté à Internet.Si les attaques de ce type, perpétrées par des botnets ont été largement étudiées par le passé, leur mode opératoire et leur contexte de mise en œuvre sont ici différents et nécessitent de nouvelles solutions. Pour ce faire, nous proposons dans le travail de thèse exposé dans ce manuscrit, une approche distribuée pour la détection à la source d'attaques DDoS perpétrées par des machines virtuelles hébergées dans un cloud public. Nous présentons tout d'abord une étude expérimentale qui a consisté à mettre en œuvre deux botclouds dans un environnement de déploiement quasi-réel hébergeant une charge légitime. L’analyse des données collectées permet de déduire des invariants comportementaux qui forment le socle d'un système de détection à base de signature, fondé sur une analyse en composantes principales. Enfin, pour satisfaire au support du facteur d'échelle, nous proposons une solution de distribution de notre détecteur sur la base d'un réseau de recouvrement pair à pair structuré qui forme une architecture hiérarchique d'agrégation décentralisée / Currently, cloud computing is a flexible and cost-effective solution widely adopted for the large-scale production of IT services. However, beyond a main legitimate usage, malicious users take advantage of these features in order to get a ready-to-use attack platform, offering a massive power. Among the greatest beneficiaries of this cloud conversion into an attack support, botclouds are used to perpetrate Distributed Denial of Service (DDoS) attacks toward any third party connected to the Internet.Although such attacks, when perpetrated by botnets, have been extensively studied in the past, their operations and their implementation context are different herein and thus require new solutions. In order to achieve such a goal, we propose in the thesis work presented in this manuscript, a distributed approach for a source-based detection of DDoS attacks perpetrated by virtual machines hosted in a public cloud. Firstly, we present an experimental study that consists in the implementation of two botclouds in a real deployment environment hosting a legitimate workload. The analysis of the collected data allows the deduction of behavioural invariants that form the basis of a signature based detection system. Then, we present in the following a detection system based on the identification of principal components of the deployed botclouds. Finally, in order to deal with the scalability issues, we propose a distributed solution of our detection system, which relies on a mesh peer-to- peer architecture resulting from the overlap of several overlay trees

High data rates and interoperability of vender devices have made WiMAX a prime desire for use worldwide. WiMAX is based on the IEEE 802.16 standard. IEEE 802.16a, b, c & d versions were updated within three years of the first launch of WiMAX. However, during those early years reports were published that highlighted the security weaknesses of the standard. These weaknesses prompted the IEEE to issue a new version, 802.16e to tackle the security issues. Despite this security enhancement, WiMAX remains vulnerable. This research project looks at the vulnerability of WiMAX 802.16e Subscriber Station/Mobile Station authentication at the initial entry and proposes approaches to the prevention of Denial of Service (DoS) attacks at this point in order to secure the Media Access Control (MAC) layer from such threats. A new protocol has been designed and developed to provide confidentiality, authentication and integrity to WiMAX users. This new protocol is integrated with Z algorithm (an algorithm described later in this paper) to provide: • Confidentiality of management messages • Message Authentication code • ID to provide for message integrity and user authentication. A simulation package was also required, to prove that a linear load of DoS attack would disable or exhaust the capacity of the base station of a WiMAX network, as well as providing other simulation functions. The freely available simulation tool NIST (NIST IPSec (Internet Protocol Security) and IKE (Internet Key Exchange) Simulation) is oriented towards fixed network communications (NIIST, 2003). There are no other relevant simulation tools; hence the purpose of this research project is to develop a new tool to simulate WiMAX security vulnerabilities and test the new protocol.

La MRAM est une technologie de mémoire non-volatile émergente, elle a la particularité de stocker les données sous forme d’orientations de moments magnétiques. Ses performances sont intéressantes et surpassent les technologies actuelles sur plusieurs aspects. Crocus Technology développe une nouvelle génération de MRAM, les TAS-MRAM (pour ThermallyAssistedSwitching MRAM). Ces MRAM ont la particularité d’effectuer les opérations d’écritures à hautes températures, améliorant ainsi la consommation électrique et facilitant sa réduction d’échelle. Les TAS-MRAM sont développées pour des applications sécuritaires ou critiques, cependant la technologie MRAM utilise des principes physiques liés aux interactions magnétiques qui sont relativement peu étudiés en termes de sécurité du composant.L’objet du travail de cette thèse est d’évaluer les potentielles faiblesses de sécurité pour cette technologie. En particulier la capacité des MRAM à garantir l’intégrité et la confidentialité des informations qui sont stockées a été étudiée. Ce travail est divisé en deux parties, une première partie est consacrée à l’analyse de la résistance des MRAM aux attaques physiques avec un focus tout particulier sur l’étude des effets des champs magnétiques sur l’écriture, la lecture et la rétention des données ainsi que les différentes solutions envisagées pour réduire ces effets. Une étude des effets de la température a également été réalisée. L’autre partie du travail porte sur l’étude des émissions électromagnétiques et l’analyse de plusieurs méthodes pour retrouver le poids de Hamming des données manipulées par la mémoire et de ce fait en extraire de potentiels secrets ou données sensibles. / MRAM (magnetoresistive RAM) is an emergent non-volatile memory technology; it has the particularity to store data in magnetic moments orientations. It has very interesting characteristics that overwhelm mature technologies on several points. Crocus Technology is developing a new MRAM technology called TAS-MRAM (for Thermally Assisted Switching). During write operations, this new MRAM technology uses a current to heat the memory cell. This reduces the power consumption and makes scalability easier. TAS-MRAM are developed for secure or critical applications but this technology relies on spintronic, a field of physics not much studied for electronics security.This work aims to evaluate potential security weaknesses of this technology. More specifically the memory capacity to guarantee data confidentiality was studied. This work was divided in two parts; one part is dedicated to the analysis of MRAM resistance against physical perturbations, with a special focus on magnetic fields (both static and pulsed) effects on read and write operations as well as their effects on data retention. Various methods to reduce these effects were tested and compared. The effect of high temperature was also studied.The second part focuses on the analysis of electromagnetic emissions of the MRAM components during its operations. Methods to retrieve the Hamming weight of data written in the memory are exposed and compared.

The objective of this study is to investigate trends in international terrorism since the end of the Cold War, including those identified as “new” terrorism and to determine to what extent these are applicable to the Al-Qaeda movement. To achieve this aim, the study focused on aspects such as the origin and development of new terrorism; the differences and resemblances between traditional and new terrorism; the historical development of international terrorism; the effect of the end of the Cold War on terrorism; and factors impacting on contemporary terrorism. An analysis of the Al-Qaeda movement was done with respect to its motivation, ideology, transnational character, target selection, operational strategy and tactics, and its desire to use non-conventional weapons. The intention was to identify aspects which may indicate whether the movement serves as a model of the characteristics identified by certain authors as a new terrorism. Case studies of the most important terrorist incidents linked to Al-Qaeda, including the September 11 attacks on the US, are included. The study demonstrates that the nature of terrorism as an instrument to obtain political objectives has evolved but, at the same time, it has retained most of its essential characteristics. An investigation of the characteristics of traditional and new terrorism confirmed this conclusion, as well as that a differentiation between these types of terrorism is mostly a matter of perspective. Another finding of the study is that terrorist campaigns have rarely obtained their strategic goals but that it nevertheless remains a popular strategy aimed at effecting desired political change. The study furthermore confirms that terrorist groups do not operate in a vacuum but are influenced by the existing political, socio-economic and cultural environments. As such the end of the Cold War has caused specific changes in the international system which facilitated the rise of a movement like Al-Qaeda and which enabled it to function at a global level. The usefulness of the study lies in the clarification of the concepts of traditional and new terrorism; its indication of the evolving of motivations and strategies applied by terrorist organisations; and in the findings about the current campaign of the Al-Qaeda movement. Copyright 2007, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. Please cite as follows: Bester, F 2007, New trends in contemporary international and transnational terrorism as manifested in the Al-Qaeda movement, MSS dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-04112008-125925/ > / Dissertation (MSS)--University of Pretoria, 2008. / Political Sciences / unrestricted

Networks of maliciously compromised computers, known as botnets, consisting of thousands of hosts have emerged as a serious threat to Internet security in recent years. These compromised systems, under the control of an operator are used to steal data, distribute malware and spam, launch phishing attacks and in Distributed Denial-of-Service (DDoS) attacks. The operators of these botnets use Command and Control (C2) servers to communicate with the members of the botnet and send commands. The communications channels between the C2 nodes and endpoints have employed numerous detection avoidance mechanisms to prevent the shutdown of the C2 servers. Two prevalent detection avoidance techniques used by current botnets are algorithmically generated domain names and DNS Fast-Flux. The use of these mechanisms can however be observed and used to create distinct signatures that in turn can be used to detect DNS domains being used for C2 operation. This report details research conducted into the implementation of three classes of classification techniques that exploit these signatures in order to accurately detect botnet traffic. The techniques described make use of the traffic from DNS query responses created when members of a botnet try to contact the C2 servers. Traffic observation and categorisation is passive from the perspective of the communicating nodes. The first set of classifiers explored employ frequency analysis to detect the algorithmically generated domain names used by botnets. These were found to have a high degree of accuracy with a low false positive rate. The characteristics of Fast-Flux domains are used in the second set of classifiers. It is shown that using these characteristics Fast-Flux domains can be accurately identified and differentiated from legitimate domains (such as Content Distribution Networks exhibit similar behaviour). The final set of classifiers use spatial autocorrelation to detect Fast-Flux domains based on the geographic distribution of the botnet C2 servers to which the detected domains resolve. It is shown that botnet C2 servers can be detected solely based on their geographic location. This technique is shown to clearly distinguish between malicious and legitimate domains. The implemented classifiers are lightweight and use existing network traffic to detect botnets and thus do not require major architectural changes to the network. The performance impact of implementing classification of DNS traffic is examined and it is shown that the performance impact is at an acceptable level.

The new and upcoming field of wireless sensor networking is unfortunately still lacking in terms of both digital forensics and security. All communications between different nodes (also known as motes) are sent out in a broadcast fashion. These broadcasts make it quite difficult to capture data packets forensically and, at the same time, retain their integrity and authenticity. The study presents several attacks that can be executed successfully on a wireless sensor network, after which the dissertation delves more deeply into the flooding attack as it is one of the most difficult attacks to address in wireless sensor networks. Furthermore, a set of factors is presented to take into account while attempting to achieve digital forensic readiness in wireless sensor networks. The set of factors is subsequently discussed critically and a model is proposed for implementing digital forensic readiness in a wireless sensor network. The proposed model is next transformed into a working prototype that is able to provide digital forensic readiness to a wireless sensor network. The main contribution of this research is the digital forensic readiness prototype that can be used to add a digital forensics layer to any existing wireless sensor network. The prototype ensures the integrity and authenticity of each of the data packets captured from the existing wireless sensor network by using the number of motes in the network that have seen a data packet to determine its integrity and authenticity in the network. The prototype also works on different types of wireless sensor networks that are in the frequency range of the network on which the prototype is implemented, and does not require any modifications to be made to the existing wireless sensor network. Flooding attacks pose a major problem in wireless sensor networks due to the broadcasting of communication between motes in wireless sensor networks. The prototype is able to address this problem by using a solution proposed in this dissertation to determine a sudden influx of data packets within a wireless sensor network. The prototype is able to detect flooding attacks while they are occurring and can therefore address the flooding attack immediately. Finally, this dissertation critically discusses the advantages of having such a digital forensic readiness system in place in a wireless sensor network environment. Copyright / Dissertation (MSc)--University of Pretoria, 2012. / Computer Science / unrestricted

Aujourd'hui, nous utilisons de plus en plus d'appareils "connectés" (téléphone portable, badge d'accès ou de transport, carte bancaire NFC, ...), et cette tendance ne va pas s'inverser. Ces appareils requièrent l'utilisation de primitives cryptographiques, embarquées dans des composants électroniques, dans le but de protéger les communications. Cependant, des techniques d'attaques permettent d'extraire de l'information du composant électronique ou fauter délibérément son fonctionnement. Un nouveau médium d'attaque, exploitant les ondes électromagnétiques est en pleine expansion. Ce médium, par rapport à des techniques de fautes à base de perturbations par faisceau LASER, propose l'avantage d’être à relativement faible coût. Nous présentons dans cette thèse la résistance d'un type de bloc cryptographique, à savoir les générateurs de nombres réellement aléatoires, aux ondes électromagnétiques. Nous montrons qu'il est possible d'extraire de l'information sensible du champ électromagnétique produit par le composant électronique, et qu'il est également possible de perturber un générateur en le soumettant à un fort champ électromagnétique harmonique / Nowadays, our society is using more and more connected devices (cellphones, transport or access card NFC debit card, etc.), and this trend is not going to reverse. These devices require the use of cryptographic primitives, embedded in electronic circuits, in order to protect communications. However, some attacks can allow an attacker to extract information from the electronic circuit or to modify its behavior. A new channel of attack, using electromagnetic waves is skyrocketing. This channel, compared to attacks based on LASER beam, is relatively inexpensive. We will, in this thesis, present a new attack, using electromagnetic waves, of a certain type of cryptographic primitive: the true random number generator. We will show that it is possible to extract sensitive information from the electromagnetic radiation coming from the electronic device. We will also show that it is possible to completly modify the behavior of the true random number generator using a strong electromagnetic field