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The Internet ecosystem comprising of thousands of Autonomous Systems (ASes) now include Internet eXchange Points (IXPs) as another critical component in the infrastructure. Peering plays a significant part in driving the economic growth of ASes and is contributing to a variety of structural changes in the Internet. IXPs are a primary component of this peering ecosystem and are playing an increasing role not only in the topology evolution of the Internet but also inter-domain path routing. In this dissertation we study and analyze the overall affects of peering and IXP infrastructure on the Internet. We observe IXP peering is enabling a quicker flattening of the Internet topology and leading to over-utilization of popular inter-AS links. Indiscriminate peering at these locations is leading to higher endto-end path latencies for ASes peering at an exchange point, an effect magnified at the most popular worldwide IXPs. We first study the effects of recently discovered IXP links on the inter-AS routes using graph based approaches and find that it points towards the changing and flattening landscape in the evolution of the Internet’s topology. We then study more IXP effects by using measurements to investigate the networks benefits of peering. We propose and implement a measurement framework which identifies default paths through IXPs and compares them with alternate paths isolating the IXP hop. Our system is running and recording default and alternate path latencies and made publicly available. We model the probability of an alternate path performing better than a default path through an IXP iii by identifying the underlying factors influencing the end-to end path latency. Our firstof-its-kind modeling study, which uses a combination of statistical and machine learning approaches, shows that path latencies depend on the popularity of the particular IXP, the size of the provider ASes of the networks peering at common locations and the relative position of the IXP hop along the path. An in-depth comparison of end-to-end path latencies reveal a significant percentage of alternate paths outperforming the default route through an IXP. This characteristic of higher path latencies is magnified in the popular continental exchanges as measured by us in a case study looking at the largest regional IXPs. We continue by studying another effect of peering which has numerous applications in overlay routing, Triangle Inequality Violations (TIVs). These TIVs in the Internet delay space are created due to peering and we compare their essential characteristics with overlay paths such as detour routes. They are identified and analyzed from existing measurement datasets but on a scale not carried out earlier. This implementation exhibits the effectiveness of GPUs in analyzing big data sets while the TIVs studied show that the a set of common inter-AS links create these TIVs. This result provides a new insight about the development of TIVs by analyzing a very large data set using GPGPUs. Overall our work presents numerous insights into the inner workings of the Internet’s peering ecosystem. Our measurements show the effects of exchange points on the evolving Internet and exhibits their importance to Internet routing.

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In dieser Arbeit ein neues bioanalytisches Konzept untersucht, das nanoskalige Zeolith-Imidazolat-Frameworks (ZIFs) als Marker für antikörperbasierte Analysemethoden einsetzt, einschließlich Enzyme-Linked-Immunosorbent-Assay (ELISA) und Lateral Flow Immunoassay (LFIA). Der Vorteil von ZIFs als Marker gegenüber etablierten Materialien ist ihre vielseitige, einfache und kostengünstige Synthese. Dazu gehört die Möglichkeit, niedermolekulare Substanzen für zusätzliche Sensorzwecke zu verkapseln und für eine hohe Selektivität stabil an Biomakromoleküle zu konjugieren. Als modellhafter Zielanalyt von Relevanz wurden Phthalat-Acylester (PAEs) ausgewählt. Die Relevanz des Nachweises von PAEs ergibt sich aus ihren Eigenschaften als endokrin wirksame Chemikalien (EDCs) und krebserregend. In Kombination mit der Tatsache, dass PAEs aufgrund ihrer Verwendung als Weichmacher in Kindergeschirr, Spielzeug, Trinkflaschen und anderen Produkten auf Polyvinylchlorid-Basis in der Umwelt reichlich vorhanden sind, zeigt, wie wichtig der routinemäßige Nachweis von PAEs in Trinkwasser oder Lebensmitteln ist. / This work explores a new bioanalytical concept that employs nanosized Zeolite Imidazolate Frameworks (ZIFs) particles as labels for antibody-based analytical methods, including enzyme-linked immunosorbent assay (ELISA) and lateral flow immunoassay (LFIA). The advantage of ZIFs as labels over established materials is their versatile, facile, and cheap synthesis. This includes the ability to encapsulate low molecular weight substances for additional sensing purposes and for stable conjugation to biomacromolecules for high selectivity. As a model target analyte of relevance Phthalate acyl esters (PAEs) have been selected. The relevance of the detection of PAEs is due to their properties as endocrine disrupting chemicals (EDCs) and carcinogenic. Combined with PAEs being abundant on the environment because of their use as plasticizers in plastic-made tableware for children, toys, drinking bottles and other polyvinylchloride-based products, shows the importance or their routine detection of drinking water or foods being so critical.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第25015号 / 工博第5192号 / 新制||工||1991(附属図書館) / 京都大学大学院工学研究科合成・生物化学専攻 / (主査)教授 古川 修平, 教授 生越 友樹, 教授 杉安 和憲 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

The need to protect information systems or assets remains crucial today. Innovations in technology have led to rapid developments and as technology continues to advance, so is the need to protect information systems. Amongst numerous effects of cyber-attacks on organizations, huge financial losses which in turn affect the economy have since been reported. Cyber security audits need to be strengthened to tighten the protection of information systems. The importance of cybersecurity audits is widely endorsed in literature. Nonetheless, frameworks used to audit cybersecurity are viewed as‘sometimes' weak links to cybersecurity due to their drawbacks in auditing cyber security. A review of literature indicated that cyber-attacks are more rampant in the African continent with the financial sector being the most targeted. Literature also highlighted that the use of relevant frameworks for auditing cyber security improves the quality and effectiveness of audits thereby enhancing cyber security. Studies in information systems have mostly looked at the adoption of frameworks, types of cyber threats and tools needed to audit. Nonetheless, it is important to note that few scholars have examined the applicability and effectiveness of the existing frameworks in auditing cyber security. Furthermore, previous studies emphasize on enhancing cyber security without a particular focus on auditing cyber security including assessing the role of the auditor during the process. As a result, this study looked at cyber security from an auditing perspective with a particular focus on the strengths and weaknesses of the current frameworks that are being used to audit cyber security including. The study also looked at the factors that enhance the effectiveness of cyber security audits. The study draws from different theories, literature and from the strengths and drawbacks of existing frameworks to create an explanatory model. To statistically test and evaluate the model, a quantitative research approach was employed to collect, analyze, and interpret data from South Africa. Data was collected using a questionnaire which was distributed to IT auditors and cyber security professionals from the Information Systems Audit and Control Association (ISACA) South African chapter members. The National Institute of Standards and Technology (NIST) cyber security framework was found to be the widely adopted framework followed by the International Organization for Standardization (ISO) standards, with the Control Objectives for Information Technologies (COBIT) being the least employed framework. The COBIT framework was found to be more aligned to Information Technology governance rather than cyber security. Furthermore, results of this study indicate that effectiveness of cyber security audits is dependent upon competencies of auditors including their ethics and integrity. Results further indicate that frameworks used for auditing are effective to some extent if properly implemented. A proper alignment of an auditor's competencies which include ethics and integrity, and an adoption of a relevant framework will result in effective cyber security audits that reduce the risks of cyber-attacks. Concerning the contribution to practice, results from this study can help organizations to determine and review focus areas of cyber security auditing that they need to emphasize and develop on. Furthermore, the developed model can be used by auditors to develop an audit plan and conduct audits that are effective in identifying, protecting, detecting, preventing, and recovering information systems or assets. The methodological, theoretical, and practical contributions are further discussed in this thesis along with limitations, recommendations, and areas for future research.

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