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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

A system for automatic positioning and alignment of fiber-tip interferometers

Jalan, Mahesh 15 November 2004 (has links)
The research described in this thesis involves the design, development, and implementation of an automated positioning system for fiber-optic interferometric sensors. The Fiber-Tip Interferometer (FTI) is an essential component in the proven Thermo-Acousto-Photonic NDE technique for characterizing a wide range of engineering materials including polymers, semiconductors and composites. The need to adapt the fiber-optic interferometric system to an industrial environment and to achieve precision control for optimizing interferometric contrast motivated the development of an automated, self-aligning FTI system design. The design enables high-resolution positioning and alignment by eliminating manual subjectivity and allows significantly improved repeatability and accuracy to be attained. Opto-electronic and electromechanical devices including a GRIN lens, 2x2 fused bi-conical taper couplers, photodiodes, motor-controlled tip/tilt stages, oscilloscopes, and a PCI card, constitute a closed-loop system with a feedback controller. The system is controlled by and communicates with a computer console using LabVIEW, a graphical language developed by National Instruments. Specifically, alignment is quantified by scanning the voltage readings at various orientations of the GRIN lens. The experimental setup specific to achieving maximum interferometric contrast intensity when interrogating silicon wafers with various surface depositions is discussed. Results corresponding to the interferometric contrast data obtained at several different standoff distances (Fizeau Cavity magnitudes) demonstrate the robustness of the novel design.
12

Augmenting Network Flows with User Interface Context to Inform Access Control Decisions

Chuluundorj, Zorigtbaatar 10 October 2019 (has links)
Whitelisting IP addresses and hostnames allow organizations to employ a default-deny approach to network traffic. Organizations employing a default-deny approach can stop many malicious threats, even including zero-day attacks, because it only allows explicitly stated legitimate activities. However, creating a comprehensive whitelist for a default-deny approach is difficult due to user-supplied destinations that can only be known at the time of usage. Whitelists, therefore, interfere with user experience by denying network traffic to user-supplied legitimate destinations. In this thesis, we focus on creating dynamic whitelists that are capable of allowing user-supplied network activity. We designed and built a system called Harbinger, which leverages user interface activity to provide contextual information in which network activity took place. We built Harbinger for Microsoft Windows operating systems and have tested its usability and effectiveness on four popular Microsoft applications. We find that Harbinger can reduce false positives-positive detection rates from 44%-54% to 0%-0.4% in IP and DNS whitelists. Furthermore, while traditional whitelists failed to detect propagation attacks, Harbinger detected the same attacks 96% of the time. We find that our system only introduced six milliseconds of delay or less for 96% of network activity.
13

Development of smartphone-based fluorescence detection system

Xiyao Wang (10688499) 27 April 2021 (has links)
Due to the huge development of technologies in past 20 years, smartphone has been through a huge evolution to be a powerful device with multi-advanced functionality. In this study, we proposed to, by utilizing the ability of CMOS camera on smartphone to capture high-quality pictures with low-light environment as the detector of fluorescence signals, to design and test a smartphone-based fluorescence detection system. Unlike the traditional fluorescence detection methods, a smartphone-based system can provide convenient, low cost and portable detection of fluorescent samples. To assist smartphone to capture clear pictures of fluorescence signal with low background noise, a portable reader that attached on the back of smartphone was designed in this study, which is a cuboid device that provides illuminance signal by using LED for exciting fluorescent samples. It also includes a plano-convex lens and a low-pass filter for the image magnification and reduce noise from surrounding light sources and light source from LED. To further improve the detection results, Noise Reduction Ensemble Averaging (NREA) algorithm was coded in Matlab to significantly enhance the fluorescence signal and reduce noise on the image results. In this study, to verify the proposed functionality of the smartphone detection system, the first experiment was conducted by using 3 different smartphone models (Galaxy S9, Pixel 3 and Oneplus One) to measure the fluorescent signal of a Nanoparticle FITC calibration slide and compare the results with the official referential results. The results from 3 smartphone models showed clear linearity that matches the referential result. To further explore the performance and detection limit of the system on fluorescent samples with lower concentrations, another 2 experiments were conducted by using FITC and Atto-550 samples as the testing objects. For FITC experiment, a 3 steps interrogation method that lowers the range of concentrations of FITC samples for 3 iterations to discover the detection limit of the system on FITC samples by using 3 different phones with different shutter times, and the detection limit is found to be 60 ppb by using Galaxy S9. For the experiment with Atto-550, hydrated and dehydrated Atto-550 samples were measured by using Galaxy S9. The results show the fluorescence signal of hydrated sample is almost unnoticeable even the concentration is 5000ppb. For the dehydrated Atto-550 samples, after 2 steps interrogation, it shows the detection limit is 7 ppb.
14

Evaluating Machine Learning Intrusion Detection System classifiers : Using a transparent experiment approach

Augustsson, Christian, Egeberg Jacobson, Pontus, Scherqvist, Erik January 2019 (has links)
There have been many studies performing experiments that showcase the potential of machine learning solutions for intrusion detection, but their experimental approaches are non-transparent and vague, making it difficult to replicate their trained methods and results. In this thesis we exemplify a healthier experimental methodology. A survey was performed to investigate evaluation metrics. Three experiments implementing and benchmarking machine learning classifiers, using different optimization techniques, were performed to set up a frame of reference for future work, as well as signify the importance of using descriptive metrics and disclosing implementation. We found a set of metrics that more accurately describes the models, and we found guidelines that we would like future researchers to fulfill in order to make their work more comprehensible. For future work we would like to see more discussion regarding metrics, and a new dataset that is more generalizable.
15

Network Intrusion and Detection : An evaluation of SNORT

Fleming, Theodor, Wilander, Hjalmar January 2018 (has links)
Network security has become a vital part for computer networks to ensure that they operate as expected. With many of today's services relying on networks it is of great importance that the usage of networks are not being compromised. One way to increase the security of a computer network is to implement a Network Intrusion Detection System (NIDS). This system monitors the traffic sent to, from and within the network. This study investigates how a NIDS called SNORT with different configurations handles common network attacks. The knowledge of how SNORT managed the attacks is used to evaluate and indicate the vulnerability of different SNORT configurations. Different approaches on both how to bypass SNORT and how to detect attacks are described both theoretically, and practically with experiments. This study concludes that a carefully prepared configuration is the factor for SNORT to perform well in network intrusion detection.
16

Secure Telemetry: Attacks and Counter Measures on iNET

Odesanmi, Abiola, Moten, Daryl 10 1900 (has links)
ITC/USA 2011 Conference Proceedings / The Forty-Seventh Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2011 / Bally's Las Vegas, Las Vegas, Nevada / iNet is a project aimed at improving and modernizing telemetry systems by moving from a link to a networking solution. Changes introduce new risks and vulnerabilities. The nature of the security of the telemetry system changes when the elements are in an Ethernet and TCP/IP network configuration. The network will require protection from intrusion and malware that can be initiated internal to, or external of the network boundary. In this paper we will discuss how to detect and counter FTP password attacks using the Hidden Markov Model for intrusion detection. We intend to discover and expose the more subtle iNet network vulnerabilities and make recommendations for a more secure telemetry environment.
17

MULTI-LEVEL ANOMALY BASED AUTONOMIC INTRUSION DETECTION SYSTEM

Al-Nashif, Youssif January 2008 (has links)
The rapid growth and deployment of network technologies and Internet services has made security and management of networks a challenging research problem. This growth is accompanied by an exponential growth in the number of network attacks, which have become more complex, more organized, more dynamic, and more severe than ever. Current network protection techniques are static, slow in responding to attacks, and inefficient due to the large number of false alarms. Attack detection systems can be broadly classified as being signature-based, classification-based, or anomaly-based. In this dissertation, I present a multi-level anomaly based autonomic network defense system which can efficiently detect both known and unknown types of network attacks with a high detection rate and low false alarms. The system uses autonomic computing to automate the control and management of multi-level intrusion detection system and integrate the different components of the system. The system defends the network by detecting anomalies in network operations that may have been caused by network attacks. Like other anomaly detection systems, AND captures a profile of normal network behavior.In this dissertation, I introduce experimental results that evaluate the effectiveness and performance of the multi-level anomaly based autonomic network intrusion detection system in detecting network attacks. The system consist of monitoring modules, feature aggregation and correlation modules, behavior analysis modules, decision fusion module, global visualization module, risk and impact analysis module, action module, attack classification module, and the adaptive learning module. I have successfully implemented a prototype system based on my multi-level anomaly based approach. The experimental results and evaluation of our prototype show that our multi-level intrusion detection system can efficiently and effectively detect and protect against any type of network attacks known or unknown in real-time. Furthermore, the overhead of our approach is insignificant on the normal network operations and services.
18

IDSAAS: INTRUSION DETECTION SYSTEM AS A SERVICE IN PUBLIC CLOUDS

Alharkan, TURKI 11 January 2013 (has links)
In a public cloud computing environment, consumers cannot always just depend on the cloud provider’s security infrastructure. They may need to monitor and protect their virtual existence by implementing their own intrusion detection capabilities along with other security technologies within the cloud fabric. Also, cloud consumers may want to collect network traffic and log them for further analysis. This can help them in writing tailor-made attacking scenarios specifically designed based on the nature of the application they want to protect. Furthermore, consumers’ applications can be distributed among different regions of the cloud or in non-cloud locations. The need to protect all these assets from a centralized location is fundamental to many cloud consumers. We provide a framework and implementation for an intrusion detection system that is suitable for the public cloud environment. The Intrusion Detection as a Service (IDSaaS) targets security of the infrastructure level for a public cloud (IaaS) by providing intrusion detection technology that is highly elastic, portable and fully controlled by the cloud consumer. These features allow cloud consumers to protect their cloud-based applications from security threats and unauthorized intruders. We developed a proof-of-concept prototype on Amazon EC2 cloud and performed different experiments to evaluate its performance. After examining the experimental results, we found that IDSaaS can provide the required protection in a reasonable and effective manner. / Thesis (Master, Computing) -- Queen's University, 2013-01-10 08:29:23.136
19

Anomaly-based correlation of IDS alarms

Tjhai, Gina C. January 2011 (has links)
An Intrusion Detection System (IDS) is one of the major techniques for securing information systems and keeping pace with current and potential threats and vulnerabilities in computing systems. It is an indisputable fact that the art of detecting intrusions is still far from perfect, and IDSs tend to generate a large number of false IDS alarms. Hence human has to inevitably validate those alarms before any action can be taken. As IT infrastructure become larger and more complicated, the number of alarms that need to be reviewed can escalate rapidly, making this task very difficult to manage. The need for an automated correlation and reduction system is therefore very much evident. In addition, alarm correlation is valuable in providing the operators with a more condensed view of potential security issues within the network infrastructure. The thesis embraces a comprehensive evaluation of the problem of false alarms and a proposal for an automated alarm correlation system. A critical analysis of existing alarm correlation systems is presented along with a description of the need for an enhanced correlation system. The study concludes that whilst a large number of works had been carried out in improving correlation techniques, none of them were perfect. They either required an extensive level of domain knowledge from the human experts to effectively run the system or were unable to provide high level information of the false alerts for future tuning. The overall objective of the research has therefore been to establish an alarm correlation framework and system which enables the administrator to effectively group alerts from the same attack instance and subsequently reduce the volume of false alarms without the need of domain knowledge. The achievement of this aim has comprised the proposal of an attribute-based approach, which is used as a foundation to systematically develop an unsupervised-based two-stage correlation technique. From this formation, a novel SOM K-Means Alarm Reduction Tool (SMART) architecture has been modelled as the framework from which time and attribute-based aggregation technique is offered. The thesis describes the design and features of the proposed architecture, focusing upon the key components forming the underlying architecture, the alert attributes and the way they are processed and applied to correlate alerts. The architecture is strengthened by the development of a statistical tool, which offers a mean to perform results or alert analysis and comparison. The main concepts of the novel architecture are validated through the implementation of a prototype system. A series of experiments were conducted to assess the effectiveness of SMART in reducing false alarms. This aimed to prove the viability of implementing the system in a practical environment and that the study has provided appropriate contribution to knowledge in this field.
20

NIDS im Campusnetz

Schier, Thomas 04 May 2004 (has links)
Workshop "Netz- und Service-Infrastrukturen" Dieser Beitrag zum Workshop "Netz- und Service-Infrastrukturen" behandelt den Aufbau eines Network Intrusion Detection System im Campusnetz.

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