Abstract

Denial of Service attacks (DOS) aim at crippling applications , servers and whole networks , disrupting legitimate users communication .In this presentation an overview of Denial of Service attack is being discussed, A detailed definition of DOS and DDOS attack is given Which is followed by different attack techniques . The Motives behind DoS attack and victim types gives a clean scenario the reasons behind the attacks and the most common targets. The seriousness of the DDoS problem and the increased frequency, sophistication and strength of attacks has led to the proposal of numerous defense mechanisms.