Information Technology Reference
In-Depth Information
Fig. 1.
Formal Security Model Structure
Fig. 2.
Real System and Formal Model Relationship
Safety Problem Resolving
Getting assurance that a system behavior will not result in an unauthorized access is
called a safety problem. In practice the safety problem can appear in the following
manner.
Safety Problem in Practice
Consider the next situation. Alice uses for her own purposes some operating system.
She is preparing a private document. Bob works at the same time with another com-
puter. He is getting multimedia from I-net. He has got a very fun music file and
wishes to send it to Alice. So, Bob asks Alice to share one of her directory. Alice has
no time and she shares the current directory where she works. Alice's operating sys-
tem has security property, but Alice shared the directory with the default access
rights. This default rights present the full control to everyone. Thus Bob can read
Alice's private document and more — change Alice's rights to access her own text.
In other example, Alice again uses for her own purposes some operating system.
Now she prohibited Bob to access her files and directories. But Alice retained the
access to the system files and executables. After running the system utilities and
changing some system files Bob can set any access right. For example, Bob can suc-
cessfully get the access by FTP to the root file system or to the registry or to the sys-
tem libraries.
