This master's thesis is meant to provide techniques in designing and building a standalone packet filtering firewall in Linux machines, mainly for small sites who don’t give much service to Internet users. It deals with attenuating the effect of the most common types of attacks using iptables. It guides how to design, implement, run, and maintain Firewall. Techniques for continuously monitoring attacks is attempted. It also give a historical, architectural and technical overview of firewalls and security attacks.

The aim of this Master's thesis is to design and to implement the security test in considering a resistance of the device under test to the effects of the distributed denial of service attack DDoS SYN Flood. After processing the test results is developed a protocol about security test of the device under test. In this thesis are tested two devices, namely CISCO ASA5510 firewall and a server with the specified name Server. The theoretical part of the thesis discusses the primary types of network attacks such as reconnaissance, gain access and denial of service attacks. Explained the concept of DoS and its principle, further types of DoS attacks and distributed denial of service attacks DDoS.

The aim of this Master thesis is a testing of Cisco ASA\,5510 firewall with affect of Denial of Service attacks. Part of the thesis is a teoretical description some of the attacks and practical tests. Practical part covers basic testing of Cisco ASA with Spirent Avalanche 3100B. Number of TCP connections per second and firewalls throughput on 7th layer of ISO/OSI model were tested. Also the effect of Denial of Service attacks on the throughput. In a next part there is described one possible way how to generate Denial of Service attacks from a Linux server to the firewall. Python scripts were used for generation DoS packets. With those scripts it is possible to generate five types of attacks.

This work deals with the security of computer networks based on TCP/IP protocol stack. The main objective is to develop a generator of DoS flooding attacks which carries out attacks such SYN flood, RST flood, UDP flood, ICMP flood, ARP flood, DNS flood and DHCP starvation. The theoretical part describes the features of the mentioned attacks and protocols or mechanisms associated with them. Next part deals with the comparison of selected tools (Hping3, Mausezahn, Trafgen) in terms of number of packets per second (pps) and the link utilization (MB/s). The practical part describes design and implementation of the new attacking tool. There is explained the importance of it’s individual modules, it’s installation and usage options. New tool is also being tested. Then there is described the development, options and installation of control interface which is in the form of web application.

abstract: Machine learning (ML) and deep neural networks (DNNs) have achieved great success in a variety of application domains, however, despite significant effort to make these networks robust, they remain vulnerable to adversarial attacks in which input that is perceptually indistinguishable from natural data can be erroneously classified with high prediction confidence. Works on defending against adversarial examples can be broadly classified as correcting or detecting, which aim, respectively at negating the effects of the attack and correctly classifying the input, or detecting and rejecting the input as adversarial. In this work, a new approach for detecting adversarial examples is proposed. The approach takes advantage of the robustness of natural images to noise. As noise is added to a natural image, the prediction probability of its true class drops, but the drop is not sudden or precipitous. The same seems to not hold for adversarial examples. In other word, the stress response profile for natural images seems different from that of adversarial examples, which could be detected by their stress response profile. An evaluation of this approach for detecting adversarial examples is performed on the MNIST, CIFAR-10 and ImageNet datasets. Experimental data shows that this approach is effective at detecting some adversarial examples on small scaled simple content images and with little sacrifice on benign accuracy. / Dissertation/Thesis / Masters Thesis Computer Science 2019

Title: Terrorism and cyberterrorism as threats for the present Objectives: Describe the principle, history and typology of terrorism. Approach and describe the problematics of cyberterrorism. Analyze and compare available terrorist attacks which happened from 11th September 2001 to 19th February 2020. Methods: The theoretical part was developed on the basis of study, analysis and research from Czech and foreign literature about problematics of terrorism and cyberterrorism. The practical pard included the collection of electronic and printed information about terrorists attacks which were further analysed and compared using five factors, which were: the year of terrorist attack, method of execution, country that tooked place of the attack, number of injured and number of victims. Results: The result of this diplama thesis is the description of the principle, history and typology of terrorism, description of problematics of cyberterrorism and analysis of terrorist attacks which happened from 11th September 2001 fo 19th February 2020. Keywords: Terrorism, terrorists, attack, cyberterrorism, threat.

Vortices are present in many fluid flows and depending on the context they may be either beneficial or harmful for different systems or processes. Planar particle image velocimetry was used to examine the vortex evolution and its decay under different turbulence intensities and vortex circulation. The vortex decayed faster in the presence of high turbulence intensity. Vortex trajectories were impacted by turbulence intensity and vortex strength. Trajectories with no turbulence intensity had less variation. The vortex wandering amplitude decreased with growth of vortex strength. The vortex decay was confined to the core of the vortex, with the tangential velocity at large radial distances from the vortex center being relatively constant in time. The vortex core radius had a greater rate of growth with the low turbulence intensity and lower angle of attack. The amplitude of fluctuation of the core circulation increased for the higher turbulence intensity and weaker vortex.

Plant fungal pathogens are a major threat to food security worldwide. The most important method of protecting plants against fungal attack is the use of fungicides, but the development of resistance towards synthetic fungicides is of great concern. Moreover, the health risks associated with the use of chemical fungicides increase the need to search for safe, efficacious and environmentally friendly fungicides. Plants produce antifungal agents by secondary metabolism to protect themselves from fungal attack, and therefore many plant species have substantial antifungal activity. The use of plant extracts could enable the development of inexpensive and environmentally acceptable fungicides based on locally available natural products. This study was undertaken to investigate weedy and invasive plant species for antifungal activity against plant pathogens in order to develop a useful product using a widely available resource. Acetone leaf extracts of seven invasive species (Chromoleana odorata, Ipomoea alba, Tecoma stans, Passiflora suberosa, Passiflora subpeltata, Aristolochia sp, Solanum seaforthianum) were screened against eight plant fungal pathogens viz Rhizoctonia solani, Fusarium oxysporium, Penicillum janthinellum, Penicillum expansum, Aspergillus parasiticus, Aspergillus niger, Pythium ultimum and Phytophthora nicotiana, using microdilution assay and bioautography. The acetone extract of Tecoma stans had reasonable antifungal activity with an average minimal inhibitory concentration (MIC) value against all the fungi of 550 ìg/ml and clear zones on bioautograms indicating inhibition of fungal growth of a compounds with an Rf of 0.082 in BEA against several of the fungal pathogens. Due to the clear compound on bioautography and availability of Tecoma stans, this species was selected for further work. Bioassay-guided fractionation of the leaves of the Tecoma stans dichloromethane (DCM) extract obtained from solvent-solvent fractionation resulted in one major compound, oleanolic acid. The isolated compound had antifungal activity with an average MIC value of 130 ìg/ml against the 10 plant pathogenic fungi and clear bands with an Rf value of 0.082 on bioautograms, indicating fungal growth inhibition. It was surprising that the MIC value of the crude DCM extract was as high as that of the only compound with antifungal activity based on bioautography. These results clearly indicated the possibility of synergisms especially since the average total activity of the extract was nearly 6.5 times higher than that of oleanolic acid with total activity values of 60154 ml for the extract and 9262 ml for oleanolic acid. Cellular cytotoxicity of DCM extract and oleanolic acid was investigated using tetrazoliumbased colorimetric assay (MTT) on Vero monkey kidney cells. The toxicity of the extract and oleanolic acid was determined by LC50 values. The DCM extract and oleanolic acid were toxic with and LC50 of 0.413 mg/ml and 0.129 mg/ml respectively, lower than that of berberine the toxic compound used as control. However therapeutic index which can be defined here as the LC50 in (ìg/ml)/MIC in (ìg/ml), indicated that though the extract and oleanolic acid were toxic, they could be used under controlled conditions against infections of certain of the fungal pathogens. The crude extract had a high therapeutic index value of 21 against microorganisms T. harzianum, R. solani, F. oxysporium and P. expansum; and oleanolic acid had high therapeutic index values of 16 and 64 of against T. harzianum and R.solani respectively. This high therapeutic index value of crude extract and oleanolic acid means that, crude extract and oleanolic acid may be used for treatment of infections by these tested fungi with very little toxicity under controlled conditions. Oleanolic acid had very low antibacterial activity (MIC >250 ìg/ml). against two Grampositive (Staphylococcus aureus, ATCC 29213 and Enterococcus faecalis, ATCC 29212) and two Gram-negative bacteria (Escherichia coli, ATCC 27853 and Pseudomonas aeruginosa, ATCC 25922). Animal pathogenic fungi were more resistant than the plant fungal pathogens. Based on the good activity of the DCM crude extract, the surprising selectivity in activity against different fungi coupled with reasonably good therapeutic indexes and the wide availability of T stans leaves opens up the possibility that a commercial product to protect plants against certain pathogens may be developed from T. stans leaves. Copyright / Dissertation (MSc (Veterinary Science))--University of Pretoria, 2008. / Paraclinical Sciences / unrestricted

We investigate so-called partitioning oracle attacks against AES-GCM and ChaCha20-Poly1305 along with some improvements. Such attacks against these two cryptosystems are efficient because they can be reduced to solving linear systems of equations over finite fields. We show, with some randomness assumptions, that such linear systems must have at least as many columns as rows. We have also chosen two finite (non-field) rings, as replacement for the respective fields used by AES-GCM and ChaCha20-Poly1305 for message authentication. These rings make the problem of linear system arrangement in a partitioning oracle attack extremely hard for large linear system dimensions.

Induced attack was studied under three conditions: (1) paired experimentally naive rats were exposed to intense electrical shock; (2) experimental subjects, previously trained to respond on a fixed vii ratio of six responses for liquid food reinforcement, were paired with target animals with the reinforcement contingency in effect; (3) experimental subjects were given a history of responding on a fixed ratio of six responses for positive reinforcement in the presence of shock, and finally this group was paired with experimentally naive targets when both the reinforcement and shock variables were present. Pairing experimental animals without shock did not cause attack, nor was bar-pressing behavior appreciably disrupted. Only when electrical shock was imposed upon pairs did attack occur. Furthermore, attack behavior severely reduced operant responding and there appeared to be no recovery of response rates over several sessions.