Access control is a major issue for application developers. An application must always be sure to protect its resources from unauthorized access. This requires properly setting permissions on created files, allowing only authorized hosts to connect to any network ports, and properly handling privilege elevation and surrendering. Applications must also defend against race conditions that may occur when opening files?for example, the Time of Check, Time of Use (TOCTOU) condition. The proper approach to access control is a consistent, careful use of all APIs that access external resources. You must minimize the time a program runs with privileges and perform only the bare minimum of operations at a privileged level. When sensitive data is involved, it is your application's duty to protect the user's data from unauthorized access; keep this in mind during all stages of development.