In a typical UNIX system, there are from 10,000 to 10,000,000 files, hundreds of simultaneously active processes, and hundreds of users. Each file and process has about 20 protection bits associated with it to allow the system to determine the accessibility of information. That means that it is not unusual to have millions of bits of protection information that have to be controlled in order for protection to be effective. In addition to the explicit protection information, there are many ``rights'' that are granted both directly and indirectly as a result of these protection bits and the available system operations.