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Vitamin C for your computer

© Thomas Williams

"Help, I think I have a virus!" says the user. The tech support person asks, "What happened?" to which the user answers, "My computer crashed." I can't count the number of times I've heard that story. With the way viruses and trojan horses are portrayed in the media, it is no wonder that people think this. The truth is that a virus or a trojan can cause a crash, but it is not so common that that should be the first thing one should think of when their system crashes.

What is a virus? In biology, a virus is a cell which attaches itself to an organism and then coerces the organism into producing copies of the virus. Commonly, this is a cold. In computer terms, a virus is a piece of code that attaches itself to other code and then either causes mayhem or produces copies of itself or both. The mayhem that can be caused ranges anywhere from unexpected crashes (hence why people think they have a virus), to destroying files on the system, to simply popping up annoying messages on the screen. Some viruses have been known to do nothing more than to do random things to a word document as the user types or rearrange shortcuts on the desktop.

There is a new breed of virus that seeks not to cause mayhem but to lie dormant on a computer. There are two types. One captures keystrokes and mouse clicks and forwards this information on to a predetermined source. The other is what is referred to as a zombie. What it does is much more insidious. It sits on a computer waiting for a specific signal. When it gets this signal, it takes it and rebroadcasts it as email messages. Spammers use this to anonymously email millions of people. They can spam with impunity, because even if the email is traced back to a source, the source is an innocuous computer that has a zombie virus program sitting on it.

What is a trojan horse? As the name suggests, it is something that appears as one thing but is really something else. Generally, a trojan horse, or trojan for short, will appear as an application of some sort. Perhaps as a self-extracting archive in an email attachment, or some great new game also contained in an email. It doesn't have to be an email attachment, but generally that is the way they are propagated. Like a virus, a trojan will make its way onto a computer and then turn around and email copies of itself to everyone in the address book on the computer. Trojans are often used as carriers for viruses. In other words, the virus is the payload and is contained within the trojan program.