But also important are your Internet browsing habits:

All these factors have a direct bearing on whether you are prone to catching viruses.

Finally, the manner in which your computer is connected to the Internet determines your susceptibility to viruses. If you have a high-speed, "always-on" Internet connection, then virus writers are actively trying to find you (or already have!). Dial-up connections are somewhat less risky - but not risk-free.

Which operating system are you using?

Microsoft's earlier versions of Windows had very little in the way of security - they conformed to Microsoft's earlier (and flawed) premise that everyone in corporations and everyone on the Internet is nice and can be trusted and that no one will do anything bad. Microsoft, by the way, has been humbled by the experience and, as a result, the newer versions of Windows are far more secure than their predecessors.

Windows 95 and Windows 98

Collectively known as Windows 9x, these earlier versions of Windows lack the basic security components found in modern operating systems. Their primary fault is that they don't separate the function of the operating system from the person who uses it. You, the computer's user, have complete control over every aspect of the computer. Even back in the '90s that wasn't too safe; if you catch a virus, the virus has the same range of control over your computer as you do.

Microsoft no longer supports Windows 95. This means that, if any security vulnerability is discovered in Windows 95, Microsoft will not issue bulletins, advice, or security patches to fix it. Not an enviable position for any user to be in.

In 2003, Microsoft announced that it would soon end support for Windows 98. But when thousands of corporate and individual computer users stormed the Microsoft castle in Redmond, Washington, armed with torches, spears, axes, and old dot-matrix printers, Microsoft relented and postponed the Windows 98 "end of life."

But for users of Windows 98, the message is clear: Your days of support from Microsoft are growing short.

Windows ME

Officially called Windows Millennium Edition or Windows ME (and playfully referred to in some circles as the Windows Miserable Edition), this is just Windows 98 with some additional features thrown in and some stability improvements. The stability improvements come at the price of higher hardware requirements, however, and Windows ME suffers from the same basic security issues as its predecessors, namely that viruses can run roughshod throughout the unprotected operating system.

Windows 2000

At long last, Microsoft had taken the kernel (insides) of Windows NT and grafted on the Windows 98 user interface (the stuff that you see on-screen when you use it), and after exhausting the world's supply of duct tape and baling wire, made it work.

Windows 2000 is a very decent operating system. It contains most of the security features that corporate customers and consumers had been requesting for a long time. Primary is the notion of "logging on" to the computer. In Windows 2000 and newer versions of Windows, if you can't log on to the computer, you can't use it. Contrast that to Windows 9x - if you can make the computer run, you can use it and do anything you want to it.

Windows XP

Windows XP contains many refinements over Windows 2000 and is even more secure. For the most part, Windows XP is an improved version of Windows 2000 and includes additional features and functions.

I've heard some say that Windows XP is just Windows 2000 with the soft, friendly interface. If you haven't seen Windows XP, it's like Windows 2000 with brighter colors and smooth, rounded corners.

Do you install security patches?

Microsoft regularly releases security patches - fixes to their software - that close security holes that could lead to virus infections. Many of these patches are deemed "critical," and a good number of them have been exploited by those chip-on-their-shoulder Internet thugs who have nothing better to do than to spread misery to as many people as possible.

Microsoft has provided a number of ways that you can use to find out about and install security patches, including Windows Update, Automatic Update, and e-mail notifications of new patches.

If you do install the critical patches that Microsoft releases, then you're in far better shape than if you have no security patches at all. Having no security patches is almost as bad as having no antivirus software: You're up the creek with a sitting duck.

I don't want you to feel bad if you're among (what I suspect is) the majority of computer users - those who have never installed security patches. Had I chosen a different career path without much chance to get familiar with computers, the thought of installing security patches would seem about as intimidating as working on my home's electrical wiring or working on a late-model automobile with all its complex wiring and safety systems. But that's what this book is for: to help get you past the reluctance.

How many people use the computer?

Are you the only person who uses your computer? Or are several colleagues, family members, or (gasp!) total strangers using your computer, like so many people sharing a germ-infested bathroom water cup?

The greater the number of people using a computer, the greater the chances are that something bad will happen. How do I know this? When several people share a complex machine like a PC, the inconsistencies in the ways that the people use the computer, and the accumulation of every user's bad habits and mistakes, can make the computer's condition deteriorate over time.

How is your computer connected to the Internet?

While there are many ways to connect to the Internet, I'm concerned with just one factor: Is your computer "always on and connected" through any sort of a broadband (high-speed) connection like DSL, a cable modem, ISDN, or satellite? Or do you use a dial-up (phone-line) connection to connect your computer to the Internet, get your e-mail, do a little surfing, and then disconnect?

It boils down to this: Is your computer always on and always connected to the Internet? If so, then your computer is far more likely to be targeted by Internet worms. Some hackers like to scan for - and find - new always-on computers.

They're looking for recruits - to see whether they can add your system to their legion of slave computers.

TECHNICAL STUFF

Let me explain this high-speed, always-on thing a little more. If your computer is connected to the Internet using a high-speed connection, then your computer is statistically more likely to be found by a scan than it would be if it were connected, say, only one or two hours per day. Statistically speaking, an always-on computer is ten times more likely to be scanned, because it's connected ten times as many hours per day. But more than that, if your computer is always on and always connected, then hackers would consider your computer more dependable. And because the connection is higher speed than dial-up, they can get more performance out of your computer for their own evil purposes.

Do you have a firewall?

A firewall, as I explain more fully in Chapter 10, is something that is designed to block the probing scans that are often associated with viruses, worms, and Trojan horses. Those people who have installed either a software firewall or a hardware firewall have far better protection than people who have neither.

A software firewall is a program that runs on your computer, invisibly (in the background), much like an antivirus program. The software firewall program carefully watches all communication coming into your computer and leaving your computer. Each network message - or packet - is examined to ascertain its type, origin, and destination. These properties are then compared to a list of rules to determine whether each packet should be allowed to pass through or not. Should the message be allowed to pass, the firewall lets it move along towards its destination. But should the message be blocked, then the firewall will not permit it to pass - and it will fail to reach its destination, like a postal letter that is intercepted in transit and simply thrown away.

A hardware firewall is an electronic appliance that is installed on a network. Its internal function is essentially similar to the software firewall, except that its protection is more centralized: All the computers on the network are protected by the hardware firewall, so none of the bad traffic on the Internet is permitted to reach any of the computers on the network.

A firewall is like a security guard at the entrance of an office building. He (or she) scrutinizes each person coming and going. He may want to look at each person's identification by examining their employee badge or other credential. If the person coming or going is carrying anything, he may ask questions about it. If the person is a guest, the guard may request that the user sign their name into a visitor's log.

The guard has a list of rules that he uses to determine whether each person coming and going will be permitted to pass through. Occasionally he will need to turn someone away, for one reason or another. He will detail each such denial so his boss can later view who was denied access and why.

Occasionally, the guard will need to call his boss and ask if a visitor is permitted to pass through (in a firewall software program, this takes the form of a pop-up window that asks if a particular program should be permitted to communicate or not).

High-risk activities

The types of activities performed on your PC also contribute to your risk, whether high or low. Each of these activities is related to how social you permit your computer to be. Do you often take it out in public where it can exchange information with other computers? In the analogy between biological viruses and computer viruses, a high degree of socialization (mingling with others) increases risk. The following sections look at some examples.

Wireless "Hot Spots"

Hoping to attract well-to-do customers, many public establishments - such as coffee houses, restaurants, and other businesses - have installed so-called Internet hot spots. These hot spots are Internet connections that a customer can use to connect to the Internet with a laptop computer, provided it's equipped with a wireless networking (also called Wi-Fi or 802.11) capability. Some establishments charge a fee for the use of their hot spots; others permit use free of charge.

People who own laptops equipped with those Wi-Fi connections can visit any of the hundreds of thousands (or perhaps millions) of Wi-Fi-equipped establishments and access the Internet to retrieve e-mail, visit Web sites, or whatever they do on the Internet. At a coffeehouse, for instance, you would purchase your tall double-shot vanilla low-fat latte and then sit down at one of the tables, turn on your laptop, and catch up on e-mail while quaffing your favorite coffee drink.

But here's the problem: These hot-spot connections have many of the same risks that are associated with always-on high-speed connections. Hackers and worms frequently scan the wireless networks in these establishments, hoping to find new victims - like, f'rinstance, your computer. Computers lacking adequate antivirus protection fall victim to the worm and become one of those zombie computers, awaiting the commands from their fiendish master.

Downloading and file sharing

If you or someone with access to your computer is doing a lot of file and program downloading and file sharing with others, chances are that sooner or later one of the files you download will be infected with a virus.

Because many viruses travel from computer to computer by hiding inside of software program files, it makes sense that the more program files you bring into your system, the more likely it will be that one of them will have a virus. Also, program files that have been copied from other computers (rather than coming directly from the manufacturer) have a much greater chance of being infected with a virus.

Instant messaging

If you are an Instant Messaging (IM) user, you are increasing your chances of catching a virus (or, of course a worm, Trojan, or other ill fate). As the popularity of IM rises, so too does this get the attention of virus writers looking for new ways to get viruses from one computer to another. Already, there have been a number of worms that have propagated themselves using IM. Every day, minute by minute, you can be sure that there will have been more such incidents.

Add-on programs

If you are the type who can't resist an online or computer store bargain, sooner or later something you pick up will have a little extra feature.

Continues...

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Excerpted from Computer Viruses For Dummies by Peter H. Gregory Excerpted by permission.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site.

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