DATABASE CONTROL ISSUES: SECURITY, BACKUP AND RECOVERY, CONCURRENCY - Fundamentals of Database Management Systems - page 296

mainframes and all disks were very large. But today, it is very possible. Flash disks
and CDs have the potential to be stolen from company offices or, for example, from
hotel rooms in which company employees on travel are staying. Laptop computers
can be stolen, too, and many have been taken by organized teams of thieves as
the laptops go through airport security stations. Even desktop computers have been
stolen from company offices.

Computer Viruses A computer virus is a malicious piece of software that is
capable of copying itself and ''spreading'' from computer to computer on diskettes
and through telecommunications lines. Strictly speaking, a computer virus doesn't
have to cause harm, but most are designed to do just that. Computer viruses have
been designed to corrupt data, to scramble system and disk directories that locate
files and database tables, and to wipe out entire disks. Some are designed to copy
themselves so many times that the sheer number of copies clogs computers and data
communications lines. Computer viruses that travel along data communications
lines are also called, ''worms.''

Damaging Computer Hardware All of the previous methods of breaching data
security have something in common: they're deliberate. However, this last category,
damaging computer hardware, can be deliberate or accidental. Even when accidental,
the issue of damaging hardware has always been considered to fall into the computer
security realm. Computers and disks can and have been damaged in many ways and
it's not been a matter of anything ''high-tech,'' either. They have been damaged or
ruined by fires, coffee spills, hurricanes, and disgruntled or newly fired employees
with hammers or any other hard objects handy. We will discuss security measures
for these problems but, in truth, no security measures for them are foolproof. That's
one of the reasons that backup and recovery procedures, as discussed later in this
chapter, are so very important.

Types of Data Security Measures
With the critical importance of data and all of the possible threats to data security, it
is not surprising that the information systems industry has responded with an array
of data security measures to protect the data and the hardware on which it is stored
and processed, Figure 11.2.

Physical Security of Company Premises In the 1950s, some progressive companies
in New York and other large cities put their mainframe computers on the ground
floor behind big picture windows so that everyone could see how, well, progressive
they were. Those days are long gone. Today, suppose your company is located in
a skyscraper it shares with other companies. Where do you put your mainframe
computer (or your several LAN servers, which are often placed in the same room for
precisely the security reasons we're talking about?) Here are some rules of thumb,
often learned from hard experience.

Don't put the computer in the basement because of the possibility of floods.

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Don't put the computer on the ground floor because of the possibility of a truck
driving into the building, accidentally or on purpose. (I know of a company that
had its computer center in a low-rise building adjoining an interstate highway.

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