 TCP targeted denial of service attack that employ number of packets for flooding the network. Thus, this attack exploits the working of TCP timer by bringing throughput of the system almost to zero. This attack generate packets only periodically in very minimal quantity. Thus the attacking packets can easily disguise with the legitimate packets and escape from the Anti- DoS traffic monitoring systems. This attack exploits the TCP timers and thus coined with the term "shrew attacks". Downloaded: 4/15/2022 9:44:49 AM Nova Southeastern University IP Address: 137.52.76.29 Analysis of Issues in SDN Security and Solutions Thus due to flooding, the congestion occur which reduces the sender's rate and corresponding potential throughput. The TCP waits for the Retransmission Time Out (RTO) to expire after which the data is sent again. The RTO timer gets double as the congestion is more in this case after which the packets are retransmitted after timer out. Thus during a low rate attack, when packets are lost, TCP enters RTO. When an attacker is able to calculate this RTO time and sends attacking packets to create packet collision and loss, the attacker can push the TCP into waiting state. Hence, there is no need for flooding the network with packets, but only send packets when the timer is about to expire and push it again into the RTO waiting time. This type of attack can effortlessly escape the traffic monitors due to its low traffic rate and is a serious challenge for the security experts. DENIAL OF SERVICE IN DETAIL When the user is denied access to resources of a particular machine, it may refer to as Denial-of-service (DoS) attack. In other words, it is the intentional block or interruption of services of a host accessing internet temporarily or permanently. Similarly, DDoS is the distributed denial of service which is intended suspension of computer and network resources in the machine of registered user. It causes the target system to stop responding to user's requests, resulting in long delays and outages. The us