Author(s): Gulshan Kumar, Amanjeet Kaur, Sania Sethi3

Network security consists of the provision and policies adopted by a network administration to prevent and monitor unauthorized access, misuse, modification, or denial of a computer network and network accessible resources. In today’s era, almost every single organization uses a computer and has a computer network to send, receive and store information. Whether it’s sending emails, storing documents, or serving information through a web server, it is very important to focus on security, especially if your network contains sensitive, confidential and personal information. So with invent and increased use of internet security has become a major concern. The entire field of network security is vast and in an evolutionary stage so main focus of this paper is on the attacks against basic principle of network security or on CIA model of security as we are aware security became a fundamental component of every network design. In this paper, we presented an overview of different network attacks on confidentiality, integrity and availability of network resources. The study will help the readers to understand the current scenario of network security and provides clues for future directions. There is a large amount of personal, commercial, military, and government information on networking infrastru cture worldwide.