Enterprise network servers and websites are exposed to a lot of attacks and attempts to hack, with the aim of sabotage or access to information. IDPS detection and prevention systems play an important role in the process of detecting and preventing hackers, and it's importance increases with the increasing experience and development of attacks and attackers. In this research, we will work to present the attacks that the network can be exposed to, then clarify the concept of cyber security, clarify the types of detection and prevention systems, mechanism and classification. in the practical part, we will apply Snort tool in the process of protecting web servers from denial of service attacks DOS.