Introduction

The Internet is composed of applications, each performing a role, whether it be routing, providing information, or functioning as an operating system. Every day sees many new applications enter the scene. For an application to truly be useful, it must interact with a user. Be it a chat client, e-commerce Web site, system command-line utility, or an online game, all applications dynamically modify execution based on user input. A calculation application that does not take user-submitted values to calculate is useless; an e-commerce system that doesn't take orders defeats the purpose.

Being on the Internet means that the application is remotely accessible by other people. If coded poorly, the application can leave your system open to security vulnerabilities. Poor coding can be the result of lack of experience, a coding mistake, or an unaccounted-for anomaly. Large applications are often developed in smaller parts consecutively, and joined together for a final project; it's possible that differences and assumptions exist in a module that, when combined with other modules, results in a vulnerability.