Information Technology Reference
In-Depth Information
CPU time and some disk space. If you are not so lucky, they may destroy valuable data
stored in your computer's file system. An invading program may even allow outsiders
to seize control of your computer. Once this happens, they may use your computer as
a depository for stolen credit card information, a Web server dishing out pornographic
images, or a launch pad for spam or a denial-of-service attack on a corporate or govern-
ment server.
7.3.1 Viruses
Viruses represent one way in which malicious code can get into a computer. A virus is
a piece of self-replicating code embedded within another program called the host [21].
Figure 7.1 illustrates how a virus replicates within a computer. When a user executes a
Virus
CPU
P
Virus
P
Q
R
File system
(a)
Virus
CPU
P
Virus
Virus
P
Q
R
File system
(b)
Virus
CPU
P
Virus
Virus
P
Q
R
File system
(c)
FIGURE 7.1 One way a computer virus can replicate. (a) A computer user executes program
P, which is infected with a virus. (b) The virus code begins to execute. It finds another
 
 
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