A firewall is used at this layer in order to prevent unauthorized users from accessing important data. Important data is data and content from the web site as well as data about the physical infrastructure. In an e-commerce environment, this important data would be credit card information about customers, wholesale pricing, and general user information. Once the firewall is in place, it will not allow users outside the firewall access this data. It functions by not allowing any traffic though to the servers unless the administrator has specifically authorized that traffic to pass. There are many firewall solutions ranging from hardware appliance solutions to software solutions running on a server.

Another example of security at this layer is traffic monitoring. This monitoring is called intrusion detection and can detect and prevent an attack on a web site or a server. This monitoring software or appliance can monitor in many different ways. One popular way is to alert an administrator of a user or process that is out of the ordinary. Intrusion detection software will log hacker information, suspicious content and even take action if a certain number of network compromises take place. This software exists so that security administrators can offer the same level of security without constantly monitoring port traffic, server logs and firewall information