A Look Into The Computer Virus


by, Michael Ross
Engineering 201.02
January 22, 1997

Most of us swap disks with friends and browse the Net looking for downloads.
Rarely do we ever consider that we are also exchanging files with anyone and
everyone who has ever handled them in the past. If that sounds like a warning
about social diseases, it might as well be.
Computer viruses are every bit as insidious and destructive, and come in a vast
variety of strains. A computer virus tears up your hard drive and brings down
your network. However, computer viruses are almost always curable diagnosed,
and cures for new strains are usually just a matter of days, not months or years,
away.

Virus, a program that "infects" computer files (usually other executable
programs) by inserting in those files\' copies of itself. This is usually done in
such a manner that the copies will be executed when the file is loaded into
memory, allowing them to infect still other files, and so on. Viruses often have
damaging side effects, sometimes intentionally, sometimes not. (Microsoft
Encarta 1996)

Most viruses are created out of curiosity. Viruses have always been viewed as a
well written, creative product of software engineering. I admit there are many
out there who create them out of malice, but far more people are just meeting a
challenge in software design. The people who make anti-virus software have much
more to benefit from the creation of new virii. This is not a slam, just an
observation. A common type of virus would be a Trojan Horse, or a destructive
program disguised as a game, a utility, or an application. When run, a Trojan
Horse does something devious to the computer system while appearing to do
something useful (Microsoft Encarta, 1996). A Worm is also a popular type of
virus. A worm is a program that spreads itself across computers, usually by
spawning copies of itself in each computer\'s memory. A worm might duplicate
itself in one computer so often that it causes the computer to crash. Sometimes
written in separate "segments," a worm is introduced secretly into a host system
either for "fun" or with intent to damage or destroy information. The term ‘
Worm\' comes from a science-fiction (Microsoft Encarta 1996).

Some viruses destroy programs on computers although, the better virii do not.
Most virus authors incorporate code that specifically destroys data after the
virus determines certain criteria have been met, that is, a date, or a certain
number of replications. Many virus do not do a good job of infecting other
programs and end up corrupting, or making the program they are trying to infect
completely unusable. The purpose of a virus, in many cases, is to infect as many
files, with little or no noticeable difference to the user.

How does a virus scanner work?

Most virus scanners use a very simple method of searching for a particular
sequence of bytes that make every virus unique, like a DNA sequence. When a new
virus is discovered, a fairly long sequence of bytes from it is inserted into
the anti-virus software database. That\'s why you need to keep them updated. Any
virus scanner you buy should handle at least three tasks: virus detection,
prevention, and removal. There are some virus scanners that use a method called
heuristic scanning. They use \'rules of thumb\' that can be used to identify some
virii that has not even been put in the virus database yet. What are the rules
of thumb? Well, they are basic assembly language clues that make the file
suspicious, such as a JMP instruction at the top of the file. No virus scanner
is infallible and anyone that tells you so have no idea what they are talking
about. The two best virus scanners in my opinion are F-PROT and THUNDERBYTE.
They use the heuristic method described above.

In conclusion; viruses are, and always will be, a part of the computing world.
They have been around since programming began and will continue to thrive as
long as computers are used. Technology will force us to adapt and be aware that
any information we place on a computer may not be safe.


References

Deadly New Computer Viruses Want To Kill Your PC usability.
By James Daley http://www.headlines.yahoo.com/news/stories
originally published in Computer Shopper December 1996

Microsoft Encarta 96; Reference Material Microsoft corporation

Category: Technology