Worm Virus —A worm virus is a program that
copies itself endlessly, tying up computer time and
eventually overloading the disk. Worms can also
spread copies of themselves over networks and disrupt
the network by overloading all the computers on the
network.
Trojan Horse Virus —A Trojan horse virus is a
program that embeds itself into other programs. When
an infected program is run, the virus further infects other
programs or causes damage to your system. Trojan
horses can contain worms or logic bombs. Once active,
the Trojan horse worm component will seek out other
programs to infect. Trojan horses are commonly used
as an initial source of infection.
Logic Bomb Virus —A logic bomb is a virus that
is embedded in a program or operating system that waits
for an event to occur. The logic bomb is activated by a
date, a time, or by some other parameter. When the
conditions of the logic bomb are met, the bomb is
activated. Logic bombs can reside undetected in a
personal computer for long periods of time, waiting for
the proper conditions to set it off. Logic bombs are
traditionally the most destructive of all viruses.
PREVENTING VIRUS INFECTIONS. —Virus
infections can be prevented with a little caution and
common sense. Viruses reside in the disk’s boot records
or in .COM or .EXE files. Your system cannot be
infected by data files. Further precautions you can use
to prevent viral attacks include:
l Never use pirated software. Most virus attacks
occur as a result of people using pirated software. Note:
Pirated software is very common in the Far East, where
it is sold complete with pirated manuals and
documentation.
l Make regular backups. Backups may be
needed to restore data files in the event of a virus
infection. Be sure to maintain several copies of your
backups. A good plan is to have one backup that is a
week old and one that is a month old. If a virus does
infect your personal computer, these backups can help
you discover when the infection happened and you can
restore some data without reintroducing the virus.
l Report all virus infections to the command’s
ADP Security Officer. The Navy is tracking all virus
infections in an attempt to discover the source of each
infection.
l Use only authorized software on personal
computers. Do not bring software from home or copy
it from other systems.
. Periodically check for virus infections. One
simple way to check for virus activity is to keep an eye
on the COMMAND.COM file in DOS. Copy the
original COMMAND.COM file under a new name that
does not contain a .COM or .EXE extension.
Periodically compare the size of this new file with the
COMMAND.COM file. If the COMMAND.COM file
has gotten larger, something caused it to grow. Suspect
a virus.
REMOVING VIRUS INFECTIONS. — If a virus
does infect your system, there are several ways to
remove it. The longest and most tedious is to low-level
format your fixed disk and restore all your files from
your backups. Another method is to use one of the
several commercial virus detection and removal
programs on the market today. These programs, when
used properly, can detect and remove viruses before
they have done permanent damage to your system.
Recovering Data After a Hardware Failure
You come to work in the morning and find that your
personal computer is dead. You haven’t made backups
of your data in the last year. Don’t panic, even after a
severe head crash some data can usually be recovered
from a fixed disk drive. Your main priority should be
to get as much data off the disk as possible, but first you
need to get it running. To do this, the first step is to
determine exactly what is wrong with the drive.
l Check the computer’s setup and ensure that the
information about the drive is still there. The setup is
stored in the computer. A battery provides power to
keep this information in the computer. If the battery
dies, when the computer tries to boot from the hard
drive, it won’t find the hard drive if the setup is gone.
l Check the temperature of the computer and the
drive. Some drives will not work if they are too hot or
too cold.
l Check the drive’s cables and connectors. Are the
connectors on tightly? Connectors can work
themselves loose, or they may not have been tightly
installed. If you have an extra set of cables, try
replacing them. A pinched cable can breakdown from
stress in time.
l Does the disk spin? If not, make the following
checks. (1) Check the power supply to see if all the
proper voltages are present. (2) Check for stiction; it is
another cause of the failure of the disk to spin properly.
Stiction can result from the lubricant on the disk getting
too hot. The heat softens the lubricant. When the drive
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