With a growth of E-commerce and availability of resources over internet number of attacks on servers providing these services, resources are also increased. Denial of service and Distributed Denial of Service are most widely launched attacks against these servers for preventing legitimate users from accessing these services. This paper presents architecture of offline Signature based Network Intrusion Detection System for detection of Denial/Distributed Denial of Service attacks against HTTP servers using distributed processing and Naïve Bayesian classifier. Experimental results are provided to prove the efficiency of proposed architecture.