What is Denial of Service

The internet is designed for processing and forwarding of any packet in a best effort manner. The packets carried by the internet may be malicious or not. Most of the time, internet architecture provides an unregulated path to victims. Denial-of-service (DoS) attack is the most common critical threat that causes devastating effects on the internet. The Botnet-based DoS attack aims to exhaust both the target resources and network bandwidth, thereby making the network resources unavailable for its valid users. The resources are utilized by either injecting a computer virus or flooding the network with useless traffic. This chapter provides a systematic analysis of the causes of DoS attacks, including motivations and history, analysis of different attacks, detection and protection techniques, various mitigation techniques, the limitations and challenges of DoS research areas. Finally, this chapter discusses some important research directions which will need more attention in the near future to guarantee the successful defense against DoS attacks.