An Investigation of Distributed Denial of Service Attacks at Application-Layer

In recent years, the online services and web applications offered by the Internet have become very popular. But Distributed Denial of Service (DDoS) attacks is atrocious threat to the application amenities. DDoS attacks are typically carried out at the network-layer and are easily defeated by the current defence mechanisms. Nowadays, DDoS attacks launched against the application-layer are most devastating in nature and are not detected by the network-layer defence methods. Therefore, detecting DDoS attacks at the application-layer has become a serious problem for the availability of application services. In this paper, a current scenario of the application-layer DDoS (ALDDoS) attacks has been presented along with its defence mechanisms. Defence mechanisms can be effective only if the attack signatures are represented in irregular user behavior.