Elementary Information Security, 3rd Edition

▶ 3.4 Security Controls for Files

Earlier is the text, we introduced the access matrix to describe access controls for processes in RAM. (See Section 2.5.) We can use the same matrix to describe access controls for files and other resources in an operating system. In general, the access matrix describes three things:

1. What we are sharing (objects)

2. With whom we share them (subjects)

3. What rights each subject has to each object

If we make very precise statements about the subjects, objects, and rights we wish to implement, then the sharing is easy to implement. If we trust the system to block all accesses except those we specifically allow, then it’s easy to verify the system’s correct behavior. The more specific and mechanical we can be in ...