This is the project which is design & development of network security in a bank using IP tables, which will improve & develop the network security of a banking system. This project is divided into three parts, Banking system, Server's configuration & Network security system. We have tried to improve the security level and server's configuration, briefly described about different types of servers like DNS, FTP, Telnet, NFS, SSH, Mail, Web, Proxy, DHCP & Samba servers, also described how to configure these servers. In network security system, we have briefly described about security system of computer network, types of security, network security, types of computer network security, process of network security, security system using Linux, the methods of providing security in Linux network, services of Linux system security & implementation security system using IP tables. Eight case studies have also implemented. Our proposed techniques will perform better in the banking system and it will ensure the security of information of banking databases. There may be some limitations. In future we will try our best to resolve these problems as well as we will submit this paper.