43.0 Security and Confidentiality
One of the main characteristics of a Linux or UNIX system is its ability to
handle several users at the same time (multiuser) and to allow these users
to perform several tasks (multitasking) on the same computer simultaneously.
Moreover, the operating system is network transparent. The users often do
not know whether the data and applications they are using are provided
locally from their machine or made available over the network.
With the multiuser capability, the data of different users must be stored
separately. Security and privacy need to be guaranteed. Data security was
already an important issue, even before computers could be linked through
networks. Just like today, the most important concern was the ability to
keep data available in spite of a lost or otherwise damaged data medium, a
hard disk in most cases.
This section is primarily focused on confidentiality issues and on ways to
protect the privacy of users, but it cannot be stressed enough that a
comprehensive security concept should always include procedures to have a
regularly updated, workable, and tested backup in place. Without this, you
could have a very hard time getting your data back—not only in the
case of some hardware defect, but also if the suspicion arises that someone
has gained unauthorized access and tampered with files.