Proposing a New Filter to Remove Impulse Noise and its Composition with PSO Algorithm to Detect and Defense against SYN Flooding Attacks

In a DoS attack can be regarded as an attempt of attackers to prevent legal users from gaining a normal network service. The TCP connection management protocol sets a position for a classic DoS attack, namely, the SYN flood attack. In this attack some sources send a large number of TCP SYN segments, without completing the third handshake step to quickly exhaust connection resources of the under attack system. This paper models the under attack server by using the queuing theory in which attack requests are recognized based on their long service time. Then it proposes a framework in which the defense issue is formulated as an optimization problem and employs combination of the particle swarm optimization (PSO) algorithm and proposed filter for reduction degradation caused by impulsive noise to optimally solve this problem. The goal is to direct the server to an optimum defense point by dynamically setting of two TCP parameters, namely, maximum number of connections and maximum duration of a half-open connection. The simulation results show that the proposed defense strategy improves the performance of the under attack system in terms of rejection probability of connection requests and efficient consumption of buffer space.