Information Technology Reference
In-Depth Information
these exist, data can no longer be considered invulnerable during
transmission. Outsiders may have an opportunity to receive data as
they move from one place to another in a network.
Coordinating Processor Security Levels: When physical channels
are secure, interprocessor security is still complicated because peo
ple generally have different capabilities and requirements on their
machines. As a simple example, someone with a personal computer
at her or his home or office may have complete freedom to access
and modify anything on that system. The owner may work with all
data and programs at will, with virtually no constraints. When that
machine is connected to a network, however, the office machine
may limit the information available through the personal computer.
The individual may need the same material both at home and in the
office, but data flow over the network may be restricted.
As the needs of users expand through a network, each machine
must monitor who is allowed to access what data, and different levels
of users enjoy different privileges. In many cases, each machine has to
trust what it is told by other machines in the network. For example, a
request for data may include the identity of the user, and a machine
receiving the message may trust that the user's identity is correct.
Frequently, on large systems on national networks, a person
with special system privileges on one machine may be given ex
panded privileges on another connecting machine. If the person is
responsible enough for one system, the assumption may be made
that she or he will be equally trustworthy on the next system. Such
an assumption may be shaky, but to limit this person's privileges
could greatly restrict the usefulness of the network and the ability
of a responsible worker to do her or his work. On the other hand,
granting these privileges also aids an intruder on one system in gain
ing access to other systems in a network. If a person breaks into one
machine (perhaps by guessing a password), that person may be able
to then break into accounts on connecting machines.
In a related problem, guessing passwords can be easier on dis
tributed systems. As a simple illustration, if one machine can inter
act with a second, then the first simply might try to log into an ac
count on the second by trial and error. If an account name is
known, for example, the first machine could simply try all possible
passwords, one after another. Such a brute force approach could
take a very long time if an account's password was a random collec
tion of characters, but the process might go quickly if a user
had chosen a simple word or name. (To reduce the possibility of a
