Distributed Denial of Service (DDoS) attack will attempt to disrupt al type of inline and virtual services of the network. The impact of this attack is so high that the DNS server will be unapproachable for around time. This attack directly malfunctioning to the neighbouring end devices and these end devices starting flooding to other nodes. The neighbouring node attacks another node and then the targeting node will attack another type of node which will be the neighbouring node. We said the nodes sometimes make a chain of infected computer that spread infected code, attachment and emails. The chain of infected computer on the real network is called a botnet. The assailants guide the botnet and control them to infect DHCP (Dynamic Host Configuration Protocol) services, DNS (Dynamic Name Services, ICMP (Internet Control messages) and so many type of services available on the current network. The victim of this type of attack targeted financial institutions, consumers and Business to consumer process. In this paper, we are review the process of DDoS, type of attack and its impact towards the network scenario. We are also explaining the defend mechanism to prevent such type of attacks in future.
Botnet, Application Layer, Network Layer, Gateway, DNS.