Distributed Denial of Service (DDoS) attacks has become a serious attack for internet security, this type of attack is the most advanced form of DoS (Denial of Service) attack. This attack can easily fake its source address, such as spoofing attack, which disguises the true origin of the attack. So, DDoS attack is the most important challenge for network security. Recent DDoS attacks will be carried out by attack tools, worms and botnets using various packet-transmission strategies and various forms of attack packets to beatattack systems. In this paper we introduced a triangular system to detect DOS attack which involves the principle of anomaly based identification in attack recognition. Detection systems based on these mechanisms willinvigilate the trafficbroadcasting over the secured networks. This may bring our solution capable of detecting known and unknown DoS attacks effectively by learning the patterns of appropriate network traffic alone. © Research India Publications.