of what security
issue you are talking about, any breach in security can be
prevented by not allowing access to the system. Now, this can be taken to
extremes by not letting anyone to have access. However, by limiting
access to the system to only authorized users, you substantially lower the risk
of breaches in security.
Keep in mind that there is no such thing as a secure
system. This is especially important when you consider that the most serious
threat comes from people who already have an account
Access control has been a part of UNIX
for a long time. It is a
fundamental aspect of any multi-user
system. The most basic form of access
control is in the form of user accounts. The only way you should be able to gain
access to a Linux system is through an account.
Users usually gain access to the
system when they have an account
set up for them. Each user is assigned an
individual password that allows the access. Access to files is determined by the
permissions that are set on the files and directories.
Access to various services such as printers or even local file systems is also
determined by permissions.
In addition, some services, as we shall see shortly can be
restricted at a much lower level.