Write Security Patterns out of this.

A military base provides a prime example of a secure location. Military personnel must be allowed in while spies, saboteurs, and reporters must be kept out. If the base has many entrances, it will be much more difficult and expensive to guard each of them. Security is easier to guarantee when everyone must pass through a single guard station.

It is hard to provide security for an application that communicates with networking, operating systems, databases, and other infrastructure systems. The application will need a way to log a user into the system, to set up what the user can and can not do, and to integrate with other security modules from systems that it will be interacting with. Sometimes a user may need to be authenticated on several systems. Additionally, some of the user-supplied information may need to be kept for later processing.