Šiuo metu yra sukurta nemažai priemonių aptikti įvairiausias DDoS atakas, tačiau siekiant sustabdyti arba bent sušvelninti DDoS atakų poveikį yra nuveikta labai nedaug. Yra labai sunku pasirinkti tinkamą DDoS atakos atrėmimo metodą. DDoS atakų atrėmimo metodų analizė galėtų padėti pasirinkti tinkamiausią metodą. „BGP DDoS Diversion“ atakų atrėmimo metodas yra vienas efektyviausių ir mažiausiai kaštų reikalaujantis metodas. Šis metodas įgyvendinamas panaudojant BGP protokolą. Ataka yra atremiama kuomet BGP protokolo pagalba yra paskelbiama tik dalis tinklo. DDoS atakos duomenų srautas tokiu atveju yra nukreipiamas į paskelbtą tinklo dalį, o kita tinklo dalis lieka nepažeista atakos. Interneto paslaugų teikėjai naudodami „BGP DDoS Diversion“ atrėmimo metodą gali apsaugoti savo tinklą nuo visiško nepasiekiamumo. Šiame tyrime buvo išnagrinėti DDoS atakų atrėmimo metodai. Išsamiai analizei buvo pasirinktas „BGP DDoS Diversion“ atrėmimo metodas. Metodo analizei buvo pasirinkta virtuali terpė. Sudaryti virtualią terpę buvo pasirinkta OPNET tinklų modeliavimo programa. Panaudojant OPNET modeliavimo įrangą, buvo sukurtas virtualus tinklas, veikiantis Interneto tinklo pagrindu. Sukurtame tinkle buvo įgyvendintas „BGP DDoS Diversion“ atakų atrėmimo metodas. Šiame darbe yra pateikta minėto atrėmimo metodo veikimo charakteristikų analizė. / Nowadays there are lot of ways how to detect various types of DDoS attacks, but in order to stop, or at least to mitigate the impact of such DDoS attacks not enough work is done. It is very difficult to choose the right DDoS mitigation method. The research of DDoS attacks mitigation can provide a good manual how to choose the most appropriate method. „BGP DDoS Diversion“ method is one of the most effective and least cost to deliver DDoS mitigation method. This method is implemented using BGP protocol. BGP diversion mechanism is used to announce a specific part of the provider‘s network to (a part of) the Internet. Announcing a specific part of this network will divert the DDoS traffic and thereby prevent other parts of the provider‘s network becoming unreachable. This gives the provider the ability to continue providing services of the rest of his custumers. This research was based on analyzing the DDoS mitigation methods. For the better analyzes the „BGP DDoS Diversion“ method was chosen. To analyze this method the virtual environment was the best way to accomplish this task. OPNET modeler software was chosen to create the virtual environment. Using OPNET the virtual network was created. Virtual network was based on Internet network standards. „BGP DDoS Diversion“ method was implemented and tested in the virtual network. This research provides the detail analyzes of „BGP DDoS Diversion“ method.

Effective management of the potential environmental impacts of naval sonar requires quantitative data on the behaviour and hearing physiology of cetaceans. Here, novel experimental and analytical methods were used to obtain such information and to test the effectiveness of an operational mitigation method for naval sonar. A Bayesian method was developed to estimate whale locations through time, integrating visual observations with measurements from on-animal inertial, acoustic, depth, and Fastloc-GPS sensors. The track reconstruction method was applied to 13 humpback whale (Megaptera novaeangliae) data sets collected during a multi-disciplinary behavioural response study in Norwegian waters. Thirty-one controlled exposure experiments with and without active transmissions of 1.3-2 kHz sounds were conducted using a moving vessel that towed a sonar source. Dose-response functions, representing the relationships between measured sonar dose and behavioural responses identified from the reconstructed tracks, predicted that 50% of the humpbacks would initiate avoidance at a relatively high received sound pressure level of 166 dB re 1 µPa. Very similar dose-response functions were obtained for cessation of feeding. In a laboratory study, behavioural reaction times of a harbour porpoise (Phocoena phocoena) to sonar-like sounds were measured using operant conditioning and a psychoacoustic method. Auditory weighting functions, which can be used to improve dose-response functions, were obtained for the porpoise based on the assumption that sounds of equal loudness elicit equal reaction time. Additional analyses of the humpback whale data set provided evidence that ramp-up of naval sonar mitigates harmful sound levels in responsive cetaceans located directly in the path of the source, and suggested that a subset of the humpback whale population, such as mother-calf pairs, and more responsive species would benefit from the use of sonar ramp-up. The findings in this thesis are intended to inform sound exposure criteria and mitigation guidelines for anthropogenic noise exposure to cetaceans.