A computer system should provide confidentiality, integrity and assurance against denial of service. However, due to increased connectivity (especially Internet), and the vast spectrum of financial possibilities that are opening up, more and more systems are subject to attack by intruders. When the computer came into existence the minimum security provided is the User Name and Password protection. Through which it is easily detected and misuse can happen very often. Later when the encryption came into existence with various encryption techniques / algorithm, the intruder can able to trace out the encrypted code. Next level of improvement is in the form of Network security. The Network security with various forms and this paper concentrates on the concept of Denial of Service attack. The paper proposes a system with a novel data structure called Partial Completion Filter(PCF), which detects a wide variety of DoS and scanning attacks that belongs to several categories (bandwidth based, claim-and-hold, port-scanning).This system can also detect bandwidth attacks that are scalable in the network.
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Intrusion Detection System, Distributed Denial of Service, PCF.