Abstract :
Computer
viruses are not inherently destructive. The essential feature of a computer
program that causes it to be classified as a virus is not its ability to
destroy data, but its ability to gain control of the computer and make a fully
functional copy of itself. It can reproduce. When it is executed, it makes one
or more copies of itself. Those copies may later be executed, to create still
more copies, ad infinitum. Not all computer programs that are destructive are
classified as viruses because they do not all reproduce, and not all viruses
are destructive because reproduction is not destructive. However, all viruses
do reproduce.
The computer virus overcomes the
roadblock of operator control by hiding itself in other programs. Thus it gains
access to the CPU simply because people run programs that it happens to have
attached itself to without their knowledge. A computer virus attaches
itself to other programs earned it the name “virus.” However that analogy is
wrong since the programs it attaches to are not in any sense alive.
A
virus is basically an executable file which is designed such that first of all
it should be able to infect documents, then it has to have the ability to
survive by replicating itself and then it should also be able to avoid
detection. Usually to avoid detection, a Virus disguises itself as a legitimate
program which the user would not normally suspect to be a Virus. Viruses are
designed to corrupt or delete data on the hard disk i.e. on the FAT (File
Allocation Table).
Viruses
are written in assembly language. High level languages like Basic, C,
and Pascal have been designed to generate stand-alone programs, but the
assumptions made by these languages render them almost useless when writing
viruses. They are simply incapable of performing the acrobatics required for a
virus to jump from one host program to another. That is not to say that one
could not design a high level language that would do the job, but no one has
done so yet. Thus, to create viruses, we must use assembly language. It is just
the only way we can get exacting control over all the computer system’s
resources and use them the way we want to, rather than the way somebody else
thinks we should.
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