Information Technology Center

There are three main types of destructive programs that affect computer systems. We hear a lot about computer viruses yet, although there are thousands of viruses not every destructive program is a virus. After reading this you will be able to differentiate between Viruses, Trojan Horses and Worms.

A Computer Virus is any computer program that is designed to replicate itself; some viruses are benign, they are simply minor annoyances or they may be invisible to most users, yet many others cause damage like deleting or corrupting files. The harmful viruses get all the media attention. For this reason it is easy to understand why most people think that all computer viruses are destructive.

A Trojan Horse is a destructive program that masquerades as a benign application; Unlike viruses, Trojan horses do not replicate themselves but they can be just as destructive. A Trojan horse may claim to rid your computer of viruses but instead introduces viruses onto your computer.

Worms are programs that spread through networks and computer operating systems quickly, without any direct action by any program or user. A worm does not require that a user attempt a boot from a floppy disk, run an infected program, or open an infected file before propogation may take place as in the case of a virus.

Where do these destructive programs come from?

Very highly skilled programmers design and develop them, then find ways to get them onto the computers of the unsuspecting. For many virus programmers it is simply a challenge particularly when they must by pass the security set up by users through ani-virus programs.

How do they work?

Viruses are intentionally designed to associate themselves with another computer program in a way that when the original programs are run, the virus program is run as well, and the virus replicates itself by attaching itself to other programs.

The Chernobyl virus was designed to be activated when the computer systems hit the 26th date each month. Many new viruses a spread as attachments to email. Email itself is a simple text message and therefore harmless, but attachments can be any type of file.

Worms take advantage of operating systems and networks to propagate extremely quickly, often with serious consequences, destroying files, slowing down systems or crashing them.

Interestingly enough, there do exist legitimate worms. They are often used for diagnostics and network utility programs.

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