Drive-by download is a sort of network attack which uses different techniques to plant malicious codes in their computers. It makes the traditional intrusion detection systems and firewalls nonfunctional in the reason that those devices could not detect web-based threats. The Crawler-based approach has been proposed by many studies to discover drive-by download sites. However, the Crawler-based approach could not simulate the real user behavior of web browsing when drive-by download attack happens. Therefore, this study proposes a new approach to detect drive-by download by sniffing HTTP flow. This study uses reputation system to improve the efficiency of client honeypots, and adjusts client honeypots to process the raw data of HTTP flow. In the experiment conducted in real network environment, this study show the performance of a single client honeypot could reach average 560,000 HTTP success access log per day. Even in the peak traffic, this mechanism reduced the process time to 22 hours, and detected drive-by download sites that users were actually browsing. Reputation system in this study is applicable to varieties of domain names because it does not refer to online WHOIS database. It established classification model on machine learning in 12 features. The correct classification rate of the reputation system applied in this study is 90.9%. Compared with other Reputation System studies, this study not only extract features from DNS A-Type but also extract features from DNS NS-Type. The experiment results show the Error Rate of the new features from DNS NS-Type is only 19.03%.

Gas turbine engines are the main propulsion source for world wide aviation and are also used for power generation. Even though they rely mainly on fossil fuel and emit climate active gasses, their importance is not likely to decrease in the future. But more efficient ways of using finite resources and hence reducing emissions have to be found. Thus, the interest to improve engine efficiency is growing. Considering the efficiency of the underlying thermodynamic cycle, an increase can be achieved by raising the turbine inlet temperature or compression ratio. Due to the complex nature of the underlying flow physics, however, the aero-thermal processes are still not fully understood. For this reason, one needs to perform research at high spatial and temporal resolution, in turn creating the need for effective means of postprocessing the large amounts of data. This dissertation addresses both sides of the problem - using high-scale, high resolution simulations as well as effective post processing techniques. As an example for the latter, a temporal highly resolved data set from wall pressure measurements of a transonic compressor stage is analyzed using proper orthogonal decomposition. The underlying experiments were performed by collaborators at Technical University Darmstadt. To decompose signals into optimal orthogonal basis functions based on temporal correlations including temperature, a formal mathematical framework is developed. A method to rank the reduced order representations with respect to heat transfer effectiveness is presented. To test both methods, a Reynolds-averaged Navier-Stokes (RANS) simulation and large eddy simulation (LES) are performed on turbulent heat transfer in a square duct with one single row of pin fins. While the LES results show closer agreement to experiments, both simulations unveil flow parts that do not contribute to heat transfer augmentation and can be considered wasteful. From the most effective mode, a wall contour for the same domain is derived and applied. In the wall contoured domain, energy in wasteful modes decreased, heat transfer increased and the temperature fluctuations at the wall decreased. Another stagnating boundary layer flow is examined in a direct numerical simulation of a first stage stator vane. Elevated levels of free stream turbulence and integral length scale are generated to simulate the features of combustor exit flow. The horseshoe vortex dynamics cause an increase in endwall heat transfer upstream of the vane. The link between energy optimal orthogonal basis functions and flow structures is examined using this data and the reduced order heat transfer analysis shows high energy modes with comparatively low impact on turbulent heat transfer. The analysis further shows that there are multiple horseshoe vortices that oscillate upstream of the blade, vanish, regenerate and can also merge. There is a punctual correlation of intense vortex dynamics and peaks in the orthogonal temperature basis function. For all data considered, the link between the energy optimal orthogonal basis functions and flow structures is neither guaranteed to exist nor straightforward to establish. The orthogonal expansion locks onto flow parts with high fluctuating kinetic energy - which might or might not be the ones that are looked for. The heat transfer ranking eliminates this problem and is valid independently of how certain basis functions are interpreted.

ENUM is the mapping of a telephone number from the PSTN to Internet services-telephone number in, URL out. It was developed as a solution to the question of how to find services on the Internet using only a telephone number. / Workshop "Netz- und Service-Infrastrukturen" ENUM = tElephone NUmber Mapping, definiert die Vorschrift, mit der eine klassische Telefonnummern auf eine Domain eindeutig abgebildet wird (dafür wird DNS genutzt). Das Ziel dabei ist, verschiedene Adressen, Nummern und URLs eines Benutzers unter einer einzigen Rufnummer verfügbar zu machen.

low about a periodic array of quasi-random distributed roughness is examined using an immersed boundary spectral method. Verification of the code used in the simulations is obtained by comparing solutions to LDA wake survey and flow visualization experiments for a periodic array of cylinders at a roughness height-based Reynolds number of 202 and a diameter to spanwise spacing d/[lambda] of 1/3. Direct comparisons for the quasi-random distributed roughness are made with experiments at roughness height-based Reynolds numbers of 164, 227, and 301. Near-field details are investigated to explore their effects upon transition. Vortices formed as the flow moves over the roughness patch create three distinct velocity deficit regions which persist far downstream. Simulated streamwise velocity contours show good agreement with experiments. Additional geometries are simulated to determine the effects of individual components of the full roughness geometry on near-field flow structures. It was found that the tallest regions of roughness determine the overall wake profile. / text

Darmstadt, Techn. Univ., Diss., 2006

University, Diss., 2006--Frankfurt (Main). / Zsfassung in engl. und dt. Sprache.

University, Diss., 2006--Giessen.

Stuttgart, Univ., Diss., 2008.

Ulm, Univ., Diss., 2008.

Hohenheim, Univ., Diss., 2008.