John works as a Network Security Professional.

John works as a Network Security Professional. He is assigned a project to test the security of www.we-are-secure.com. He is working on the Linux operating system and wants to install an Intrusion Detection System on the We-are-secure server so that he can receive alerts about any hacking attempts. Which of the following tools can John use to accomplish the task?

Each correct answer represents a complete solution. Choose all that apply.