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VIRUS
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1989-04-19
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Computer Virus Myths
by Rob Rosenberger
with Ross Greenberg
A number of myths have popped up recently about the threat
of computer "viruses". There are myths about how widespread they
are, how dangerous they are, and even myths about what a computer
virus really is. We'd like the facts to be known.
The first thing you have to understand is that a virus is a
programming technique that falls in the realm of "Trojan horses."
All viruses are Trojan horses, but very few Trojan horses can be
called a virus.
That having been said, it's time to go over the terminology
we use when we lecture:
BBS Bulletin Board System. If you have a modem, you
can call a BBS and leave messages, transfer com-
puter files back & forth, and learn a lot about
computers. (What you're reading right now most
likely came to you from a BBS, for example.)
Bug an accidental flaw in the logic of a computer
program that makes it do things it shouldn't
really be doing. Programmers don't mean to put
bugs in their program, but they always creep in.
The first bug was discovered by pioneer Grace
Hopper when she found a dead moth shorting out a
circuit in the early days of computers. Pro-
grammers tend to spend more time debugging their
programs than they do writing them in the first
place.
Hacker someone who really loves computers and who wants
to push them to the limit. Hackers don't release
Trojan horses onto the world, it's the wormers who
do that. (See the definition for a "wormer".)
Hackers have a healthy sense of curiosity: they
try doorknobs just to see if they're locked, and
they tinker with a piece of equipment until it's
"just right."
Shareware a distribution method for quality software avail-
able on a "try before you buy" basis. You pay for
the program only if you find it useful. Shareware
programs can be downloaded from BBSs and you are
encouraged to give an evaluation copy to friends.
There are few advertising & distribution costs, so
many shareware applications can rival the power of
off-the-shelf counterparts, at just a fraction of
the price.
Copyright (c) 1988 Rob Rosenberger & Ross Greenberg Page 1
Trojan horse a generic term describing a set of computer
instructions purposely hidden inside a program.
Trojan horses tell a program to do things you
don't expect it to do. The term comes from a
historic battle in which the ancient city of Troy
was offered the "gift" of a large wooden horse
that secretly held soldiers in its belly. The
Trojans rolled it into their fortified city....
Virus a term for a very specialized Trojan horse that
can spread to other computers by secretly
"infecting" programs with a copy of itself. A
virus is the only type of Trojan horse which is
contagious, like the common cold. If it doesn't
meet this definition, then it isn't a virus.
Worm a term similar to a Trojan horse, but there is no
"gift" involved. If the Trojans had left that
wooden horse outside the city, they wouldn't have
been attacked -- but worms can bypass your
defenses. An example is an unauthorized program
designed to spread itself by exploiting a bug in a
network software package. (Such programs could
possibly also contain a virus that activates when
it reaches the computer.) Worms are usually
released by someone who has normal access to the
computer or network.
Wormers the name given to the people who unleash
destructive Trojan horses. Let's face it, these
people aren't angels. What they do hurts us.
They deserve our disrespect.
Viruses, like all Trojan horses, are purposely designed to
make a program do things you don't expect it to do. Some viruses
are just an annoyance, perhaps only displaying a "Peace on earth"
message. The viruses we're worried about are the ones designed
to destroy your files and waste the valuable time you'll spend to
repair the damage.
Now you know the difference between a virus and a Trojan
horse and a bug. Let's get into some of the myths:
All purposely destructive code comes as a virus.
Wrong. Remember, "Trojan horse" is the general term for
purposely destructive code. Very few Trojan horses are actually
viruses.
All Trojan horses are bad.
Believe it or not, there are a few useful Trojan horse tech-
niques in the world. A "side door" is any command not documented
in the user manual, and it's a Trojan horse by definition. Some
programmers install side doors to help them locate bugs in their
Computer Virus Myths Page 2
programs. Sometimes a command may have such an obscure function
that it makes sense not to document it.
Viruses and Trojan horses are a recent phenomenon.
Trojan horses have been around since the first days of the
computer. Hackers toyed with viruses in the early 1960s as a
form of amusement. Many different Trojan horse techniques were
developed over the years to embezzle money, destroy data, etc.
The general public wasn't aware of this problem until the IBM PC
revolution brought it into the spotlight. Just five years ago,
banks were still covering up computerized embezzlements because
they believed they'd lose too many customers.
Computer viruses are reaching epidemic proportions.
Wrong again. Viruses may be spread all over the planet but
they aren't taking over the world. There are only about fifty or
so known virus "strains" at this time and a few of them have been
completely eliminated. Your chances of being infected are slim
if you take proper precautions. (Yes, it's still safe to turn on
your computer!)
Viruses could destroy all the files on my disks.
Yes, and a spilled cup of coffee will do the same thing. If
you have adequate backup copies of your data, you will be able to