This article discusses various ways data gets into your program, emphasizing how to deal appropriately with them; you might not even know about them all! It first discusses how to design your program to limit the ways data can get into your program, and how your design influences what is an input. It then discusses various input channels and what to do about them, including environment variables, files, file descriptors, the command line, the graphical user interface (GUI), network data, and miscellaneous inputs.

This article shows how to validate input -- one of the first lines of defense in any secure program.

This column explains how to write secure applications; it focuses on the Linux operating system, but many of the principles apply to any system. In today's networked world, software developers must know how to write secure programs, yet this information isn't widely known or taught. This first installment of the Secure programmer column introduces the basic ideas of how to write secure applications and discusses how to identify the security requirements for your specific application. Future installments will focus on different common vulnerabilities and how to prevent them.