Компьютерные вирусы

Computer viruses

Introduction

In my presentation, I will tell about viruses - so that you can learn how they work and also understand how to protect yourself from computer infections.

Computer viruses are mysterious and grab our attention. On the one hand, viruses show us how vulnerable we are. On the other hand, they show how sophisticated human beings have become. But what exactly is a virus? To answer this question I would like to draw an analogy with biological virus.

What's a "Virus"?

Computer viruses are called viruses because they share some of the traits of biological viruses. A computer virus passes from computer to computer like a biological virus passes from person to person.

There are similarities at a deeper level, as well. A biological virus is not a living thing. A virus is a fragment of DNA inside a protective jacket. A biological virus must inject its DNA into a cell. The viral DNA then uses the cell's existing machinery to reproduce itself.

A computer virus shares some of these traits. It must piggyback on top of some other program or document in order to get executed. Once it is running, it is then able to infect other programs or documents. This is where you can see an analogy.

Types of Infection

Now, I would like to represent you the types of virus, or if correctly, types of computer infection. There are many different forms of electronic infection. And the most common are:

• Viruses - A virus is a small piece of software that piggybacks on real programs. For example, a virus might attach itself to a program such as a spreadsheet program. Each time the spreadsheet program runs, the virus runs, too, and it has the chance to reproduce (by attaching to other programs) or wreak havoc.
• E-mail viruses - An e-mail virus moves around in e-mail messages, and usually replicates itself by automatically mailing itself to dozens of people in the victim's e-mail address book.
• Worms - A worm is a small piece of software that uses computer networks and security holes to replicate itself. A copy of the worm scans the network for another machine that has a specific security hole. It copies itself to the new machine using the security hole, and then starts replicating from there, as well.
• Trojan horses - A Trojan horse is simply a computer program. The program claims to do one thing (it may claim to be a game) but instead does damage when you run it (it may erase your hard disk). Trojan horses have no way to replicate automatically.

How They Spread

To prevent from these computer infections, firstly, you should understand how they spread.

Early viruses were pieces of code attached to a common program like a popular game or a popular text editor. Any virus is designed to run first when the legitimate program gets executed. It loads itself into memory and looks around to see if it can find any other programs on the disk. If it can find one, it modifies it to add the virus's code to the unsuspecting program. Then the virus launches the "real program." The user really has no way to know that the virus ever ran. Unfortunately, the virus has now reproduced itself, so two programs are infected. The next time either of those programs gets executed, they infect other programs, and the cycle continues.

The spreading part is the infection phase of the virus. Viruses wouldn't be so violently despised if all they did was replicate themselves. Unfortunately, most viruses also have some sort of destructive attack phase, where they do damage. Some sort of trigger will activate the attack phase, and the virus will then "do something bad" - anything from printing a silly message on the screen to erasing all of your data. The trigger might be a specific date, or the number of times the virus has been replicated, or something similar.

As virus creators got more sophisticated, they learned new tricks. One important trick was the ability to load viruses into memory so they could keep running in the background as long as the computer remained on. This gave viruses a much more effective way to replicate themselves.

So what measures can prevent you from viruses? There are simple.

            An Ounce of Prevention

You can protect yourself against computer viruses with a few steps:

• If you are truly worried about traditional viruses, you should be running a more secure operating system based on UNIX core. Linux, as example. You never hear about viruses on these operating systems because the security features keep infections (and unwanted human visitors) away from your hard disk.
• If you are using an unsecured operating system, then buying virus protection software is a nice safeguard.
• If you simply avoid programs from unknown sources (like the Internet), and instead stick with commercial software purchased on CDs, you eliminate almost all of the risk from traditional viruses
• You should make sure that Macro Virus Protection is enabled in all Microsoft applications, and you should NEVER run macros in a document unless you know what they do. There is seldom a good reason to add macros to a document, so avoiding all macros is a great policy.