Security is essential to all types of applications, including web applications. Would you use Facebook if anyone could update your status by impersonating you? If that were possible, then no one would come back to Facebook. From this example, we can see that security is not so much a feature as it is a necessity for all applications.

In this chapter, we are going to learn about the following topics:

When we talk about the security of an application, we primarily want to prevent any unauthorized access, meaning that only the people who have access to the information should be able to access it—nothing more, nothing less.

Before proceeding further, I would like to clarify some of the core concepts regarding security.