Are Computer Viruses Still A Bad Idea

Are Computer Viruses Still A Bad Idea Essay, Research Paper VirusAre “Good” Computer Viruses Still a Bad Idea?During the past six years, computer viruses have caused unaccountable amount of damage – mostly due to loss of time and resources. For most users, the term “computer virus” is a synonym of the worst nightmares that can happen ontheir system. Yet some well-known researchers keep insisting that it is possible to use the replication mechanism ofthe viral programs for some useful and beneficial purposes.This paper is an attempt to summarize why exactly the general public appreciates computer viruses as somethinginherently bad. It is also considering several of the proposed models of “beneficial” viruses and points out theproblems in them. A set of conditions

is listed, which every virus that claims to be beneficial must conform to. At last, a realistic model using replication techniques for beneficial purposes is proposed and directions are given in which this technique can be improved further.The paper also demonstrates that the main reason for the conflict between those supporting the idea of a “beneficial virus” and those opposing it, is that the two sides are assuming a different definition of what a computer virus is.1. What Is a Computer Virus?The general public usually associates the term “computer virus” with a small, nasty program, which aims to destroy the information on their machines. As usual, the general public’s understanding of the term is incorrect. There are many kinds of destructive or otherwise malicious

computer programs and computer viruses are only one of them. Suchprograms include backdoors, logic bombs, trojan horses and so on [Bontchev94]. Furthermore, many computerviruses are not intentionally destructive – they simply display a message, play a tune, or even do nothing noticeable at all. The important thing, however, is that even those not intentionally destructive viruses are not harmless – they are causing a lot of damage in the sense of time, money and resources spent to remove them – because they are generallyunwanted and the user wishes to get rid of them.A much more precise and scientific definition of the term “computer virus” has been proposed by Dr. Fred Cohen in his paper [Cohen84]. This definition is mathematical – it defines the computer virus as a

sequence of symbols on thetape of a Turing Machine. The definition is rather difficult to express exactly in a human language, but an approximateinterpretation is that a computer virus is a “program that is able to infect other programs by modifying them to include a possibly evolved copy of itself”.Unfortunately, there are several problems with this definition. One of them is that it does not mention the possibility of a virus to infect a program without modifying it – by inserting itself in the execution path. Some typical examples are the boot sector viruses and the companion viruses [Bontchev94]. However, this is a flaw only of the human-language expression of the definition – the mathematical expression defines the terms “program” and “modify”in a way that

clearly includes the kinds of viruses mentioned above.A second problem with the above definition is its lack of recursiveness. That is, it does not specify that after infecting a program, a virus should be able to replicate further, using the infected program as a host. Another, much more serious problem with Dr. Cohen’s definition is that it is too broad to be useful for practical purposes. In fact, his definition classifies as “computer viruses” even such cases as a compiler which is compiling its own source, a file manager which is used to copy itself, and even the program DISKCOPY when it is on diskette containing the operating system – because it can be used to produce an exact copy of the programs on this diskette.In order to understand the reason of the above