What Are Viruses and Worms, and Why You May Be At Risk, Even If You Think You're Safe

Everybody has heard of computer viruses and worms - they're all over the news these days, but many people don't really understand what they are, or how to avoid them.

Basically, a virus or a worm is a program which is able to copy itself and spread from computer to computer. Kind of like a virus in a person, which gets one person sick, then that person passes it on to others, and they get sick too. Hence the name virus.

The difference between a worm and a virus is that a virus needs a person to open it to start it running and to allow it to infect your computer (for example, by opening an email attachment that hasn't been scanned for viruses) A worm on the other hand, infect a computer and spread to other computers again and again without you clicking a single thing.

Once a worm or a virus is on your computer, it can do a lot of different things. Until fairly recently, viruses (from now on, just assume that any time I say viruses, that I mean both viruses and worms, because they're very similar and it'll save time) Until recently, viruses were usually very damaging - they would delete files, completely erase hard drives, or sometimes even ruin a computers' motherboard by infecting a specific chip on the motherboard. (A motherboard, also called a "main logic board", is the main circuit board in the computer, so it's kind of like your central nervous system) When the software in the chip was replaced, you suddenly couldn't boot the computer, even with a clean hard drive.

Viruses were so damaging because the virus writers mainly wrote them to get their name known, and the bigger the damage, the more infamous they were.

These days, many viruses can lurk on your computer without you even knowing it, because the virus writers have different agendas. For example, there are millions of computers out there which are infected with viruses that cause the computers to send out spam (junk mail), and the computer owner has no idea this is happening.

These days, virus writers want to make money, and so to allow the virus to spread the most, the infected computers need to keep working. Because of this, the computer may slow down some, but nothing major seems to have gone wrong. But in reality, the computer user has had the wool pulled over their eyes and they just keep clicking away innocently while their computer silently sends out millions of junk emails.

By some estimates, there are over 100,000 viruses which specifically infect Windows PCs. These specific viruses cannot infect Linux or Unix machines, or Macs. There is literally one virus (at the time I'm recording this) which can infect some Macs running OS X, but it is pretty much what they call a "concept virus" which isn't likely to spread "in the wild."

So if you use a Mac, you are a lot safer than your friends who use Windows. But just because there aren't any Mac viruses now, doesn't mean someone won't develop one in the future. It is harder to do this for a Mac than it is to do for a Windows machine, because of the way the Mac software is designed, but it's hardly impossible.

On the other hand, Symantec (who makes Norton Antivirus) estimates that 91% (yes, that's ninety-one percent) of Windows computers are infected with some malicious software. Although this estimate includes adware and spyware (which I cover in a different chapter of this report) that's still an incredibly high number.

There are a couple of reasons for why viruses and other "malware" infect Windows machines so often. One reason is exposure - there are many times more computers running Windows than any other operating system, so they present a bigger target. But remember, just because a lot of people use something, doesn't mean it's the best option. Fast food is very very popular, but I don't think you could really say it's the best quality food.

Speaking of food, if you know your history, then you may have heard of the Irish Potato Famine that killed hundreds of thousands of people back in the 1800s.

This happened because of something called a "monoculture." In plain English, what that means is, the Irish used potatoes as the core of their diet - everybody ate them, and everybody grew them. And they were all growing one just one breed of potato.

What does that have to do with computers, you might be wondering.

Well, because they were only growing one type of potato, when a disease came along, it spread like wildfire, and killed off all of the potatoes, since they were all of the same type, and all had the same weakness to this disease.

This is just like how most people are using Windows, which creates something called a "computing monoculture." So that latest virus or worm, spreads all over the world sometimes in a matter of hours, because most computers are vulnerable.

Does that make sense?

And aside from that, Windows has so many security flaws (which mostly happen because of programming mistakes made by Microsoft) that they're discovering dozens and dozens more of these critical flaws every year. Any one of these critical flaws can allow anyone with a little knowledge to take control of your computer and use it any way they want. Or they can write a program (a virus) which does the same thing. For each of these flaws, you must install the update or "patch," which fixes the flaw, or you run the risk of your computer being hacked or infected.

Mac OS X in contrast to Windows, has had some of it's own security flaws in the last few years, but as yet we haven't seen a single real threat to them. Other operating systems such as Linux have similar track records. It is just as important on these computers to install any security updates, too, just in case.

Bottom line is, if you're running Windows it is absolutely essential that not only do you have antivirus software installed, but you must make sure your one-year subscription hasn't expired, and the software is updated every day. Your computer may have antivirus software installed, but if the subscription has expired, it's not protecting you!

I see this all the time -- people with Dells, HPs, or most of the big brand names will find their computer came with Norton or McAfee antivirus, but it only works for 90 days before the subscription expires. People get prompted to renew their subscription, but they don't do it.

I have been called by so many people, especially in the last few years, who have had me clean their systems up for them. In most cases I've found they either never put antivirus software on their PCs, or had ignored the repeated warnings from Norton or McAfee telling them their subscription had expired.

In many of those cases, I discovered a computer that barely worked anymore (or was so slow it literally took 10-20 minutes before you could start using it after you turned it on). In these situations I'm faced with either wiping their computer clean, and spending hours reinstalling Windows and their various programs (assuming they even had all their disks), etc., or spending hours scanning and cleaning up the computer with a variety of programs just to get them working again. Either way it takes time and effort to recover from a bad virus infection.

Hundreds of dollars, and hours, days, or weeks of aggravation, just because they didn't spend $40-$50 for antivirus software and take a few minutes to install it.

Another critical mistake people make with their antivirus software, is assuming that because Norton Antivirus and McAfee Antivirus are two of the best known, and most popular programs, that they are also the best ones.

This turns out not to be true. In fact, just the opposite.

A recent study by CERT, the Computer Emergency Response Team (one of the world's leading computer security organizations) revealed that the most popular antivirus programs, which include Norton and McAfee, missed 80% of new malicious software!

So in other words, 80% of the time, those programs are useless when trying protecting your computer!

So you're much better off with a less-known, but high quality program like Kaspersky Internet Security, which has been consistently rated as one of the best, with a success rate of over 99% effective. It's also a really good deal as you get a license to use it on 3 computers for less than the price of Symantec Antivirus (Norton) on one PC.

Aside from having effective antivirus software, which is current and up-to-date, you also need to be getting your security updates installed as soon as they come out.

On Windows computers, this is called Windows Update, and on Macs this is called Software Update.

Both Macs and Windows users (if you have Windows XP service pack 2 installed or any newer version of Windows) probably have their computer checking for these updates automatically, but they may not get installed unless you follow the steps when the computer tells you there are updates available.

Hopefully these tips will help you keep yourself safe.

Worth Godwin is a computer coach with over 15 years' experience helping computer users of all levels, and has also worked for many years "in the trenches" as a hardware and software tech, solving real-world computer problems.

Worth has also been studying the human mind, and how people learn, since the early 1990s. He draws upon all of this experience, as well as his English and writing degrees, to teach people in a unique way with explanations that really make sense.

In 2006, Worth began putting his easy lessons together on CD, helping you with either Apple Mac training or Windows computer training that lets you go at your own pace, for an affordable price, with a system that is both simple and easy.