Types of Computer Viruses

When you listen to the news, you hear about many different forms of electronic infection. The most common are:

Viruses - a virus is a tiny 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).

E-mail viruses - an e-mail virus move around in email messages, and usually replicate itself by automatically mailing itself to dozens of people in the victim's e-mail address book.

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 cannot automatically replicate.

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.

Let’s learn a bit about viruses, and see how we can protect ourselves against them.

The best way to start is with admitting the truth: People created viruses. Out there are people who do more than play games or watch TV shows. Out there are a few people that find a pleasure in ruining somebody’s day, or even somebody’s computer.

A computer virus is a computer program that can copy itself and infect a computer without permission or knowledge of the user. The original one may modify the copies, or the copies may modify themselves, as in a human body virus, so it is harder to be traced and deleted.

A virus cannot move by itself from one computer to another, it can only spread when its host is taken to the uninfected computer, for instance, a user sending it over a network or carrying it on a removable medium such as a floppy disk, CD, or USB drive.

In studying computer viruses you will be amazed of how many interesting things you can discover and see! Viruses have some interesting points. On the one hand, viruses show us how vulnerable we are. On the other hand, they show how sophisticated and interconnected human beings have become.

Computer viruses are called viruses because they share some of the traits of biological viruses. A computer virus passes from computer to computer as 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. Unlike a cell, a virus has no way to do anything or to reproduce by itself -- it is not alive. Instead, a biological virus must inject its DNA into a cell. The viral DNA then uses the cell's existing machinery to reproduce itself. In some cases, the cell fills with new viral particles until it bursts, releasing the virus. In other cases, the new virus particles bud off the cell one at a time, and the cell remains alive. A computer virus must piggyback on top of some other program or document and once it is running, it is then able to infect other programs or documents.

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

Another trick was the ability to infect the boot sector of the hard disk or floppy disc. The boot sector is a small program, which is the first part of the operating system the computer loads. The boot sector contains a small program that tells the computer how to load the rest of the operating system. By putting its code in the boot sector, a virus can is guaranteed to be "at work" each time the computer is on.

If you can, try to use more safe operating systems, like UNIX. If you use Windows, a good idea is to buy some protective software, like antivirus programs and firewalls. Also, never double on an attachment that contains an executable file.

We live in a world where both computer and biological viruses are surrounding us. I don’t believe we will ever find a way to completely stop them. Even if we will, until then the only way is to protect ourselves.