This bachelor thesis deals with the denial of service incidents. The first half of the thesis presents the most important terms that are later used in the thesis. These terms are: incident, cyber attack, ISO 27035, denial of service attacks and distributed denial of service attacks. The first half of the thesis then describes typical profile of those who perpetrate denial of service attacks and their usual motives. Finally, the first half of the thesis displays several approaches to clasification of denial of service attacks. The second half at first describes and analyzes selected methods of denial of service attacks. The second half of the thesis then analyzes defense against denial of service attacks. Using the afforementioned analysis, ...