Transmission Control Protocol (TCP) is a popular transport protocol used by several applications including Web based services. TCP is a connection oriented protocol that uses a three-way handshake to establish a TCP connection before application data exchange starts to take place. TCP SYN attack occurs when a host sends a large number of TCP/SYN packets to the target system. Each TCP SYN packet is handled like a connection request, causing the server to send back a TCP/SYN-ACK to acknowledge the connection request also maintaining the state of this connection. The server now waits for the third packet in TCP handshake from the host initiating the connection. However, because it is not a legitimate host that initiated the connection, the third packet needed to complete the TCP handshake never arrives. These half-open connections exhausts the resources at the server, keeping it from responding to connection requests from legitimate users.