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Canadian Computer Consulting
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First, some background on viruses. The first viruses were usually more annoyances than anything else. One very famous virus, in the early days of PCs, was called the "Yankee Doodle Virus". It did nothing more and nothing less than to play "Yankee Doodle" periodically over your PC Speaker. Most viruses these days are quite a bit more harmful, and a lot more intelligent. There are also "worms" and "trojans", which are technically somewhat different than viruses, but for now let's call them all viruses. The first thing a virus typically tries to do is to destroy your anti-virus software. You may wonder why you paid for anti-virus software if it can simply be destroyed by a virus, but there is a simple explanation. New viruses are written each day, often several a day, and some of them spread very fast. A well-written virus can infect millions of computers within 24 hours of being released. It typically takes 3 or 4 days before a company like Norton can make a "cure", and your anti-virus software might only check for updates every 2 or 3 days. Symantec, for example, only generally releases automatic updates once a week. That means that more often that not your computer is completely unprotected from any virus created within the past week. During this time, the virus could sneak into your computer and destroy your anti-virus software. Sometimes the only warning you'll have that you have a virus is when your anti-virus software says "disabled", and you can't turn it back on again. The second thing a virus will try to do is to spread itself. Usually this means either sending copies of itself to everybody you've ever sent an email to or received an email from, or sending itself out using instant messenger clients such as MSN Messenger or AOL Instant Messenger. Often an intelligent virus will pluck two names at random (let's call them person A and person B) from your email, and send it to person A disguised as if it came from person B. That way person A will yell at person B (who likely doesn't even have the virus), and no-one will be able to warn you (person C) that you have a virus. Some especially nasty viruses will destroy personal files on your computer, or even prevent Windows from running at all. These viruses aren't very common, however, as parasites who rapidly kill their host can't have a very long life-span. More often the virus will simply destroy or disable certain programs or portions of Windows. Simply put, a virus can do anything to your computer that its creator can envision. A little bit now about worms, trojans, and viruses, and why they're different. Viruses require some form of human input in order to spread. You have to check your email, or put an infected disk in your drive, or accept a transfer from someone on instant messenger. Notice I said all you have to do is check your email in order to get a virus. Until recently, the advice was that you couldn't get a virus unless you opened an attachment that had a virus in it. While that is still true in most cases, there have been several instances lately of viruses that can infect your computer by using "features" in your email client without you having to open anything at all. Simply the act of opening your email program is sometimes enough for the virus to be able to spread. The best thing you can do to prevent such viruses from infecting your computer is to ensure that you always have the latest updates from Microsoft (www.WindowsUpdate.com) and to ensure that your anti-virus protection is always up to date. Worms are very similar to viruses, except that they spread themselves differently. A worm doesn't need to use e-mail or messenger clients in order to spread. In fact, a worm can spread itself extremely rapidly because it doesn't need any human input in order to spread. Because most people in the world use the Windows operating system, most worms are written to use Windows. Windows is an extremely complicated piece of software, with millions of features available in it for use by you and your programs. All it takes is for someone malicious to find a "bug" in one of these features and they can often find a way to use that bug to automatically spread their worm. Microsoft, of course, will try to fix the bug as quickly as possible, and most computers will automatically check with Microsoft for "bug fixes" every single day. But again, as was the problem with anti-virus software, there is a delay between the worm being written, and the cure being implemented. Simply speaking, a trojan is a worm or virus that includes a piece of code in it that opens a "back door" into your computer. If someone (presumably the person that wrote the trojan) knows where to look for that back door, they can access whatever information they want on your computer. This is, of course, only if you're connected to the internet. Sometimes a trojan will simply sit quietly on your computer in anticipation of a planned synchronized attack at some date and time in the future. A "firewall", such as the one built into Windows XP, can often prevent the spread of worms and the use of most trojans by stopping outside access to your computer. If you are using a firewall, people outside of your local network (house or business) usually can't even tell that you're online. These "software firewalls" can be disabled by a virus, however. If you have a "router" for your home network, that makes a more reliable firewall than any software can provide, and will prevent outsiders and worms from hacking into your computer. That said, there are many things a software firewall does better than a "hardware" firewall. Software firewalls can help prevent worms and viruses from spreading if you are already infected, can often detect and delete SPAM, and can certainly work in conjunction with a hardware firewall to provide an extra layer of protection for your computer. The best solution is to always use and keep up to date a software firewall and antivirus software, to ensure Windows is updated (automatically!) on a daily basis, and to install a hardware router that can act as a firewall. Also, and I know you've all heard this one before but it is critically important, never open attachments unless you know what they are and who they're from! |
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