DDoS Attack and Defense Scheme in Wireless Ad hoc Networks

The wireless ad hoc networks are highly vulnerable to distributed denial of service(DDoS) attacks because of its unique characteristics such as open network architecture, shared wireless medium and stringent resource constraints. These attacks throttle the tcp throughput heavily and reduce the quality of service(QoS) to end systems gradually rather than refusing the clients from the services completely. In this paper, we discussed the DDoS attacks and proposed a defense scheme to improve the performance of the ad hoc networks. Our proposed defense mechanism uses the medium access control (MAC) layer information to detect the attackers. The status values from MAC layer that can be used for detection are Frequency of receiving RTS/CTS packets, Frequency of sensing a busy channel and the number of RTS/DATA retransmissions. Once the attackers are identified, all the packets from those nodes will be blocked. The network resources are made available to the legitimate users. We perform the simulation with Network Simulator NS2 and we proved that our proposed system improves the network performance. Wireless networks are inherently susceptible to security problems. The intrusion on the transmission medium is easier than for wired networks and it is possible to conduct denial of service attacks by scrambling the used frequency bands. The ad hoc context increases the number of potential security vulnerabilities. Ad hoc networks can not benefit from the security services offered by dedicated equipment such as firewalls, authentication servers and so on. The security services must be distributed, cooperative and consistent with the available bandwidth. One of the serious attacks to be considered in ad hoc network is DDoS attack. A DDoS attack is a large-scale, coordinated attack on the availability of services at a victim system or network resource. The DDoS attack is launched by sending an extremely large volume of packets to a target machine through the simultaneous cooperation of a large number of hosts that are distributed throughout the network. The attack traffic consumes the bandwidth resources of the network or the computing resource at the target host, so that legitimate requests will be discarded. A bandwidth depletion attack is designed to flood the victim network with unwanted traffic that prevents legitimate traffic from reaching the victim system. A resource depletion attack is an attack that is designed to tie up the resources of a victim system. This type of attack targets a server or process at the victim making it unable to legitimate requests for service. Any amount of resources can be exhausted with a sufficiently strong attack. The only viable approach is to design defense mechanism that will detect the attack and respond to it by dropping the excess traffic. The DoS attacks that target resources can be grouped into three broad scenarios. The first attack scenario targets Storage and Processing Resources. This is an attack that mainly targets the memory, storage space, or CPU of the service provider. Consider the case where a node continuously sends an executable flooding packet to its neighborhoods and to overload the