Polymorphic & Cloning Computer Viruses
generation of today is growing up in a fast-growing, high-tech world which
allows us to do the impossibilities of yesterday. With the help of modern
telecommunications and the rapid growth of the personal computer in the average
household we are able to talk to and share information with people from all
sides of the globe. However, this vast amount of information transport has
opened the doors for the computer "virus" of the future to flourish.
As time passes on, so-called "viruses" are becoming more and more
adaptive and dangerous. No longer are viruses merely a rarity among computer
users and no longer are they mere nuisances. Since many people depend on the
data in their computer every day to make a living, the risk of catastrophe has
increased tenfold. The people who create computer viruses are now becoming much
more adept at making them harder to detect and eliminate. These so-called "polymorphic"
viruses are able to clone themselves and change themselves as they need to avoid
detection. This form of "smart viruses" allows the virus to have a
form of artificial intelligence. To understand the way a computer virus works
and spreads, first one must understand some basics about computers, specifically
pertaining to the way it stores data. Because of the severity of the damage that
these viruses may cause, it is important to understand how anti-virus programs
go about detecting them and how the virus itself adapts to meet the ever
changing conditions of a computer. In much the same way as animals, computer
viruses live in complex environments. In this case, the computer acts as a form
of ecosystem in which the virus functions. In order for someone to adequately
understand how and why the virus adapts itself, it must first be shown how the
environment is constantly changing and how the virus can interact and deal with
these changes. There are many forms of computers in the world; however, for
simplicity’s sake, this paper will focus on the most common form of personal
computers, the 80x86, better known as an IBM compatible machine. The computer
itself is run by a special piece of electronics known as a microprocessor. This
acts as the brains of the computer ecosystem and could be said to be at the top
of the food chain. A computer’s primary function is to hold and manipulate
data and that is where a virus comes into play. Data itself is stored in the
computer via memory. There are two general categories for all memory: random
access memory (RAM) and physical memory (hard and floppy diskettes). In either
of those types of memory can a virus reside. RAM is by nature temporary; every
time the computer is reset the RAM is erased. Physical memory, however, is
fairly permanent. A piece of information, data, file, program, or virus placed
here will still be around in the event that the computer is turned off. Within
this complex environment, exists computer viruses. There is no exact and
concrete definition for a computer virus, but over time some commonly accepted
facts have been related to them. All viruses are programs or pieces of programs
that reside in some form of memory. They all were created by a person with the
explicit intent of being a virus. For example, a bug (or error) in a program,
while perhaps dangerous, is not considered a computer virus due to the fact that
it was created on accident by the programmers of the software. Therefore,
viruses are not created by accident. They can, however, be contracted and passed
along by accident. In fact it may be weeks until a person even is aware that
their computer has a virus. All viruses try to spread themselves in some way.
Some viruses simply copy clones of themselves all over the hard drive. These are
referred to as cloning viruses. They can be very destructive and spread fast and
easily throughout the computer system. To illustrate the way a standard cloning
virus would adapt to its surroundings a theoretical example will be used. One
day a teacher decides to use his/her classroom Macintosh’s Netscape to
download some material on photosynthesis. Included in that material is a movie
file which illustrates the process. However, the teacher is not aware that the
movie file is infected with a computer virus. The virus is a section of binary
code attached to the end of the movie file that will execute its programmed
operations whenever the file is accessed. Then, the teacher plays the movie. As
the movie is being played the virus makes a clone of itself in every file inside
the system folder of that computer. The teacher shuts down the computer
normally, but the next day when it is booted up all of the colors are changed to
black and white. The explanation is that the virus has been programmed to copy
itself into all of the files that the computer accesses in a day. Thus, when the
computer reboots, the Macintosh operating system looks into the system folder at
a file to see how many colors to use. The virus notices it access this file and
immediately copies it self into it and changes the number of colors to two. Thus
the virus has detected a change in the files that are opened in the computer and
adapted itself by placing a clone of itself into the color configuration files.
Another prime way that viruses are spread throughout computers extremely rapidly
is via LANs (Local Area Networks) such as the one setup at Lincoln that connects
all of the classroom Macs together. A LAN is a group of computers linked
together with very fast and high capacity cables. Below is an illustrated
example of a network of computers: Since all of the computers on a network are
connected together already, the transportation of a virus is made even easier.
When the "color" virus from the above example detects that the
computer is using the network to copy files across the school, it automatically
clones a copy of itself into every file that is transported across the network.
When it reaches the new computer it waits until it has been shut off then turned
back on again to copy itself into the color configuration files and change the
display to black and white. If this computer should then log on to the network,
the virus will transport again. In this manner network capable viruses can very
quickly adapt and cripple an entire corporation or office building. Do to the
severity of some viruses, people have devised methods of detecting and
eradicating them. The anti-viral programs will scan the entire hard drive
looking for evidence that viruses may have infected it. These programs must be
told very specifically what to look for on the hard drive. There are two main
methods of detecting viruses on a computer. The first is to compare all of the
viruses on the hard disk to known types of viruses. While this method is very
precise, it can be rendered totally useless when dealing with a new and
previously unknown virus. The other method deals with the way in which a common
cloning virus adapts. All that a cloning virus really does is look at what
operations the computer is executing and react and adapt to them by making more
copies of itself. This is the serious flaw with cloning viruses: all the copies
of itself look the same. Basically all data in a computer is stored in a byte
structure format. These bytes, which are analogous to symbols, occur in specific
orders and lengths. Each of the cloned viruses has the same order and length of
the byte structure. All that the anti-virus program has to do is scan the hard
drive for byte structures that are duplicated several times and delete them.
This method is an excellent way of dealing with the adaptive and reproducing
format of cloning viruses. The disadvantage is that it can produce a number of
false alarms such as when a user has two copies of the same file. Thereby, a
simple cloning viruses’ main flaw is exposed. However, the (sick minded)
people who create these viruses have founded a way to get around this by
creating a new and even more adaptive virus called the polymorphic virus.
Polymorphic viruses were created with the explicit intent of being able to adapt
and reproduce in ways other than simple cloning. These viruses contain a form of
artificial intelligence. While this makes them by no means as smart or adaptive
as a human being, it does allow them to avoid conventional means of detection. A
conventional anti-virus program searching for cloned viruses will not think
files with different byte-structures as are viruses. A good analogy for a
polymorphic virus would be a chameleon. The chameleon is able to change its
outward appearance but not the fact that it is a chameleon. A polymorphic
virus’s main goal is just like that of any other virus: to reproduce itself
and complete some programmed task (like deleting files or changing the colors of
the monitor); this fact is never changed. However, it is the way in which they
reproduce that makes them different. A polymorphic virus does more to adapt than
just make copies of itself into other files. In fact, it does not really even
clone its physical byte structure. Instead it creates other programs with
different byte structures that are attempting to perform the same task. In a
sense, polymorphic viruses are smart enough to evolve itself by writing new
programs on the fly. Because of the fact that they all have different byte
structures, they pass undetected through conventional byte comparison anti-viral
techniques. Not only are polymorphic viruses smart enough to react to their
environment by adaptation, but they are able to do it in a systematic way that
will prevent their future detection and allow them to take on a new life of
their own. Computer viruses are extremely dangerous programs that will adapt
themselves to the ever changing environment of memory by making copies of
themselves. Cloning viruses create exact copies of themselves and attach to
other files on the hard drive in an attempt to survive detection. Polymorphic
viruses are able to change their actual appearance in memory and copy themselves
in much the same way that a chameleon can change colors to avoid a predator. It
is not only the destructive nature of computer viruses that make them so
dangerous in today’s society of telecommunications, but also their ability to
adapt themselves to their surroundings and react in ways that allow them to
proceed undetected to wreck more havoc on personal computer users across the
globe.

Bibliography
Rizzello, Michael. Computer Viruses. Internet. http://business.yorku.ca
/mgts4710/rizello/viruses.htm Solomon, Dr. Alan. A Guide to Viruses. Internet.
http://dbweb.agora.stm.it/ webforum/virus/viruinfo.htm Tippett, Peter S. Alive!
Internet. http://www.bocklabs.wisc.edu/~janda/alive10.html. 1995. "Virus
(computer)," Microsoft (R) Encarta. Copyright (c) 1993 Microsoft
Corporation. Copyright (c) 1993 Funk & Wagnall's Corporation Yetiser, Tarkan.
Polymorphic Viruses. VDS Advanced Research Group. Baltimore, 1993.