Sürdürülebilir Yeşil Kampüs Koleksiyonu / Sustainable Green Campus Collection

Permanent URI for this collectionhttps://hdl.handle.net/11147/7755

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Access Right: Open AccessAuthor: search.filters.author.Aytaç, İsmail Sıtkı

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Now showing 1 - 3 of 3
  • Master Thesis
    Intrusion Detection System Alert Correlation With Operating System Level Logs
    (Izmir Institute of Technology, 2009) Toprak, Mustafa; Aytaç, İsmail Sıtkı
    Internet is a global public network. More and more people are getting connected to the Internet every day to take advantage of the Internetwork connectivity. It also brings in a lot of risk on the Internet because there are both harmless and harmful users on the Internet. While an organization makes its information system available to harmless Internet users, at the same time the information is available to the malicious users as well. Most organizations deploy firewalls to protect their private network from the public network. But, no network can be hundred percent secured. This is because; the connectivity requires some kind of access to be granted on the internal systems to Internet users. The firewall provides security by allowing only specific services through it. The firewall implements defined rules to each packet reaching to its network interface. The IDS complements the firewall security by detected if someone tries to break in through the firewall or manages to break in the firewall security and tried to have access on any system in the trusted site and alerted the system administrator in case there is a breach in security. However, at present, IDSs suffer from several limitations. To address these limitations and learn network security threats, it is necessary to perform alert correlation. Alert correlation focuses on discovering various relationships between individual alerts. Intrusion alert correlation techniques correlate alerts into meaningful groups or attack scenarios for ease to understand by human analysts. In order to be sure about the alert correlation working properly, this thesis proposed to use attack scenarios by correlating alerts on the basis of prerequisites and consequences of intrusions. The architecture of the experimental environment based on the prerequisites and consequences of different types of attacks, the proposed approach correlates alerts by matching the consequence of some previous alerts and the prerequisite of some later ones with OS-level logs. As a result, the accuracy of the proposed method and its advantage demonstrated to focus on building IDS alert correlation with OS-level logs in information security systems.
  • Master Thesis
    Time synchronization in wireless sensor metworks
    (Izmir Institute of Technology, 2008) Kulaklı, Ali Burak; Aytaç, İsmail Sıtkı
    In this thesis, an enhanced synchronization algorithm for Wireless Sensor Networks is proposed. This algorithm uses TPSN (Timing-sync protocol for sensor networks) as a base synchronizer and does modifications on it to achieve a better synchronization with a lower message overhead. Basically, there are three improvements that can be applied onto TPSN, which are clustering the network, chain synchronization among nodes and adaptive synchronization interval. In the first phase of the thesis, a simulation environment is provided for TPSN using pthreads on a Linux computer. This environment helps understanding the parameters that TPSN relies on and testing the algorithm in different simulated environments with different characteristics using the enhancements onto TPSN algorithm. In the second phase, ns2 simulator environment is used to get more precise results and test the modifications. Finally, latest modifications are done on TPSN and all the results are gathered from ns2.
  • Master Thesis
    A Dominating Set Based Communication Architecture for Distributed Applications in Mobile Ad Hoc Networks
    (Izmir Institute of Technology, 2007) Çokuslu, Deniz; Aytaç, İsmail Sıtkı
    In this thesis, we aim to design and implement algorithms in a distributed environment in order to solve clustering, backbone formation and efficient routing problems for mobile ad hoc networks(MANET)s. Our first goal is to find a connected dominating set (CDS), then construct clusters using the clusterhead information and extend this approach to multi-level clusters. We propose a new Connected Dominating Set based clustering algorithm for clustering in MANETs. Our algorithm is based on Wu and Li's algorithm, however we provide significant modifications and heuristics such as considering the degrees of the nodes during marking process. We also extend our algorithm in order to generate a hierarchy of clusters. Our second goal is to implement a flooding based routing mechanism on top of CDS based clusters. We propose a two level flooding mechanism by using the CDS members as the gateways of the clusters. We describe the algorithms, analyze their time and message complexities and measure their performance in the simulation environments.