Basically in order to provide users with ease of access High Performance Computing (HPC) systems gives unrestricted use of its internal network. Although adequate access control (without encryption) always be applied, HPC systems does not provide a method to authenticate administrative access by network administrator, thus opening possible cyber threats in the future. This study proposes the utilization of Port Knocking technique in order to hide administrative access of Firewall external attackers. Our experiments show an improved security mechanism by HPC admin both for SSH and FTP services.