Along with the growth of the computer system and networks, the mysterious and malicious threats and attacks on the computer systems are also increasing exponentially. There is a need of continuous evaluation of the security of a network and enhancement of the network attack detection system, which will be able to detect different attacks along with the characteristics of the attacks. In previous work, the port scan attack is considered as precursors to an attack and the target was to provide the mitigation technique for the particular port scan attack. There have been relatively few empirical studies done for port scan related attacks and those that do exist may no longer reflect the impact of such attacks on the functionalities of the UTM/network device and on the network. To address this lack of knowledge, this experiment is carried out in fully controlled test bed environment wherein a set of varieties of attack can be simulated and impact of attack(s) is analyzed and appropriate mitigation technique is suggested to mitigate the port scan attack. The experiment result indicates that the port scan mitigation implementation on UTM helps reducing the load on the UTM device and reduces network congestion effectively.