All users of a system would normally have a userid and an associated set of rules to access resources. The rules may occasionally allow access to the same resource such as a file for sharing of data between two users. The administrator of a system normally has access to all resources on a system. The single userid which has access to all resources on an operating system creates a single point of failure, one need only discover the password or exploit a programming fault in order to gain access to all resources and hence circumvent the privacy which is expected by the general user. The description of holes in a system is often better known amongst individuals attracted to this sort of game that it is by the administrators who are in charge of the system.
Ethernet is a shared medium much like a party-line in a rural telephone system .
The above table represents a hypothetical example of what might be found in a set of rules in a simple central privacy system. Anyone who can gain access to the above table can gain access to all the resources of the system. The above example is quite simply and is often modified slightly by defining a function which scrambles the password in a unique way and which is not reversible. The scrambled values for the password are then stored in the table and someone who gains access to the table cannot determine the value of the password to be entered at logon because of the nature of the function Scramble. Although our table is more secure it is still quite weak.