Abstract of dissertation

Introduction

We live in time when mankind has come into the era of scientific and technical revolution. To the end of the 20-th century people revealed a lot of secrets of substance and energy transformation and succeeded in using such knowledge for making their life better.

Beside substance and energy there is another component, which plays significant role in people s life- that is information that implies various messages, skills, knowledge, news. Special devices appeared in the past century. These are computers, developed for information keeping and transforming that resulted in computer revolution. Nowadays PC mass using, unfortunately, is tied up with self-creating program viruses which impede normal computer functioning, which destruct disk file structure and damage information kept in computer.

Despite laws passed in many countries against computer crimes and development of special protection program against virus, quantity of new program viruses is constantly growing. It demands of PC user knowledge of virus nature, ways of contamination and protection.

Computer viruses, properties and classification.

Nowadays PC s are used where an user gets free access to the all machine resources. Namely this point has granted the possibility for danger, which is called computer virus.

What is computer virus? Formal definition of this notion is not created yet and there is serious doubt thatit can be done at all.

Numerous attempts to give "modern" definition of virus have collapsed. To understand the problem complicity try to define, for example, editor. You either invent something very common or start to mention all known types of editor. Both can hardly be acceptable. That is why we will limit ourselves by consideration of some computer viruses properties, which allow us to talk about them as definite program type. First of all, virus is a program. Such a simple affirmation by itself is capable to ruin lots oflegends about outstanding computer virus abilities. Virus is capable to turn over an image on your monitor but its not capable to turn over the monitor. You should not take into consideration the legend about virus-killer " which annihilates operators by means of showing the deathly coloured gamma of the 25-th shot". Unfortunately, some authoritative editions publish "hot news from computer fronts" which finally are the consequence of not really clear subject understanding. Virus is the program which can self create. Such capability is the only treit, which belongs to all the viruses. But not only viruses are capable for self-creation. Any operational system and lots of programs can create their own copies. The virus copies are not obliged to correspond to the original but can be quiet different! Viruses can not exist in "entire isolation", nowadays, it is impossible to imagine a virus which does not use code of other programs, file structure information or just other programs names. The reason is simple: virus is to conquer the control by any way.

Trojans are the programs fulfilling beside the functions described in documentation some other function bound up with security breakage and destructive actions. There are events when such programs were created to facilitate virus expansion. Lists of the aforementioned programs are widely published in foreign mass media. Usually marks also contain some information which damage BC, but function, on the contrary, tries to be imperceptible, thus the more time a program will not provoke any suspension the more time a mark will work.

If Trojan and virus damage by means of avalanchelike self -creation or obvious destruction, the main function of the virus like "worm" is breakage of the attacked system i.e. protection conquering with the aim of security and integrity breakage.

This process can be automatized by means of virus which is called network worm.

Worms are viruses, which expand through global networks damaging the whole system and not single programs. This is the most dangerous type of virus, thus attack objects in this case are informational systems of state scale. Since global network Internet has appeared this type of security breakage is the most dangerous because at any time, any 40 million computers connected to Internet can be attacked. Signs of virus getting.

- work finishing or incorrect functioning of previously good working programs,

- slow computer functioning,

- impossibility of operational system loading,

- disappearance of files and catalogues or distort of their content,

- time and date of file modification changing,

- file size changing,

- unexpected significant files increase on disk,

- significant size decrease of free operative memory,

- showing on the monitor unforeseen messages and images,

- unforeseen sound signals,

- frequent and malfunction of computer.

It is important to note that the aforementioned events are not obviously created by virus. They can be a consequence of other reasons. That is why the correct diagnostics of the computer is always difficult.