If we move air away from heat sink, it will take heat energy with it. A fan mounted on heat sink is used to move air. This method of heat transfer is called convection. Eventually all air inside computer case will get hot, so fans are used to blow air out of case of computer.

The heat has moved from CPU, to heat sink, to air inside case, to air in room where you're sitting at your computer desk. The room starts to get hot, and eventually air conditioner turns on.

You can view an air conditioner as a "pipe". A fan blows hot air from your room through fins that transfer heat to a liquid. The liquid is piped to fins outside house. A fan blows cooler outside air past fins to remove heat from liquid.

The air conditioner has an evaporator valve that changes liquid to a gas after heat is removed. In a gas, molecules are further apart than in a liquid. This causes it to cool down quite a bit more. The gas goes through fins inside house, picking up heat. It is then compressed into a liquid to concentrate heat so outside fins can remove heat more efficiently.

Shuttle's I.C.E. (Integrated Cooling Engine) Heat Pipe uses a very similar method to cool a CPU. The CPU has a heat sink with copper heat pipes. The heat of CPU causes liquid coolant inside heat pipe to change to a gas. Convection created by pressure of gas moves coolant to a second heat sink where a fan is used to blow heat out of computer's case. Releasing heat causes coolant to change back to a liquid. Gravity then carries coolant back to CPU heat sink.

One last method of heat transfer we haven't discussed yet is radiation. Some of heat of CPU and heat sink is released as infrared radiation. Similar to light (although invisible to human eyes), radiation strikes insides of computer case, causing it to get warm. Ultimately computer case itself acts as a heat sink conducting heat to outside air.

This article explains three ways - conduction, convection, and radiation - that heat is transported from a computer CPU to air outside computer case. You now understand thermodynamics of a computers and why it is important to maintain its various components.

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So if I were you, I’d click on View on toolbar in your Outlook or Outlook Express and close preview pane. (You have to click on View and then Layout in Outlook Express.)

On a network at work? You could get a virus that way. Worms are viruses that come into your computer via networks, Kuo said. They travel from machine to machine and, unlike, classic viruses, they attack machine itself rather than individual files.

Worms sit in your working memory, or RAM, Nachenberg said.

OK, so we’ve talked about how viruses get into a computer. How do they cause so much damage once they’re there?

Let’s say you’ve caught a classic virus, one that replicates and attacks various files on your computer. Let’s go back to example of virus that initially infects your Microsoft Word program.

Well, it might eventually cause that program to crash, Nachenberg said. It also might cause damage to your computer as it looks for new targets to infect. This process of infecting targets and looking for new ones could eventually use up your computer’s ability to function, he said.

Often destruction a virus causes is pegged to a certain event or date and time, called a trigger. For instance, a virus could be programmed to lay dormant until January 28. When that date rolls around, though, it may be programmed to do something as innocuous but annoying as splash popups on your screen, or something as severe as reformat your computer’s hard drive, Nachenberg said.

There are other potential reasons, though, for a virus to cause your computer to be acting slow or in weird ways. And that leads us to a new segment – reason virus writers would want to waste their time creating viruses in first place.

The majority of viruses are still written by teenagers looking for some notoriety, Nachenberg said. But a growing segment of virus-writing population has other intentions in mind.

For these other intentions, we first need to explain “backdoor” concept.

The sole purpose of some viruses is to create a vulnerability in your computer. Once it creates this hole of sorts, or backdoor, it signals home to mama or dada virus writer (kind of like in E.T.). Once virus writer receives signal, they can use and abuse your computer to their own likings.

Trojans are sometimes used to open backdoors. In fact that is usually their sole purpose, Kuo said.

Trojans are pieces of code you might download onto your computer, say, from a newsgroup. As in Trojan War they are named after, they are usually disguised as innocuous pieces of code. But Trojans aren’t considered viruses because they don’t replicate.

Now back to real viruses. Let’s say we have Joe Shmo virus writer. He sends out a virus that ends up infecting a thousand machines. But he doesn’t want feds on his case. So he instructs viruses on various machines to send their signals, not of course to his computer, but to a place that can’t be traced. Hotmail email happens to be an example of one such place, Kuo said.

OK, so virus writers now control these computers. What will they use them for? One use is to send spam. Once that backdoor is open, they bounce spam off of those computers and send it to other machines, Nachenberg said.

That’s right. Some spam you have in your email right now may have been originally sent to other innocent computers before it came to yours so that it could remain in disguise. If authorities could track down original senders of spam, they could crack down on spam itself. Spam senders don’t want that.

Ever heard of phishing emails? Those are ones that purport to be from your internet service provider or bank. They typically request some information from you, like your credit card number. The problem is, they’re NOT from your internet service provider or your bank. They’re from evil people after your credit card number! Well, these emails are often sent same way spam is sent, by sending them via innocent computers.

Of course makers of anti-virus software use a variety of methods to combat onslaught of viruses. Norton, for instance, uses signature scanning, Nachenberg said.

Signature scanning is similar to process of looking for DNA fingerprints, he said. Norton examines programming code to find what viruses are made of. It adds those bad instructions it finds to its large database of other bad code. Then it uses this vast database to seek out and match code in it with similar code in your computer. When it finds such virus code, it lets you know!

©2004 by Kara Glover