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All About Computer Viruses |
by:
Kara Glover |
Feel Free to reprint this article in newsletters and on websites, with resource box included. If you use this article, please sendbrief message to let me know where it appeared: karathreethreethree@earthlink.net
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URL: http://www.karathecomputertutor.com
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Date of copyright: November twozerozerofour
All About Computer Viruses
by Kara Glover
karathreethreethree@earthlink.net
Your computer is as slow as molasses. Your mouse freezes every onefive minutes, and that Microsoft Word program just won’t seem to open.
You might havevirus.
Just what exactly isvirus? What kind is in your computer? How did it get there? How is it spreading and wreaking such havoc? And why is it bothering with your computer anyway?
Viruses are pieces of programming code that make copies of themselves, or replicate, inside your computer without asking your explicit written permission to do so. Forget getting your permission down on paper. Viruses don’t bother to seek your permission at all! Very invasive.
In comparison, there are pieces of code that might replicate inside your computer, say something your IT guy thinks you need. Butcode spreads, perhaps throughout your office network, with your consent (or at least your IT guy’s consent). These types of replicating code are called agents, said Jimmy Kuo,research fellow with McAfee AVERT,research arm of anti-virus software-maker McAfee Inc.
In this article, though, we’re not talking aboutgood guys, oragents. We’ll be talking aboutbad guys,viruses.
A long, long time ago in computer years, like five, most viruses were comprised ofsimilar breed. They entered your computer perhaps throughemail attachment orfloppy disk (remember those?). Then they attached themselves to one of your files, say your Microsoft Word program.
When you opened your Microsoft Word program,virus replicated and attached itself to other files. These could be other random files on your hard drive,files furthest away from your Microsoft Word program, or other files, depending on howvirus writer wantedvirus to behave.
This virus code could contain hundreds or thousands of instructions. When it replicates it inserts those instructions, intofiles it infects, said Carey Nachenberg, Chief Architect at Symantec Research Labs,arm of anti-virus software-maker Symantec. Corp.
Because so many other types of viruses exist now,kind just described is calledclassic virus. Classic viruses still exist but they’re not quite as prevalent as they used to be. (Perhaps we could put classic viruses onshelf with Hemingway and Dickens.)
These days, inmodern era, viruses are known to spread through vulnerabilities in web browsers, files shared overinternet, emails themselves, and computer networks.
As far as web browsers are concerned, Microsoft’s Internet Explorer takes most ofheat for spreading viruses because it’s used by more people for web surfing than any other browser.
Nevertheless, “Any web browser potentially has vulnerabilities,” Nachenberg said.
For instance, let’s say you go towebsite in IE you have every reason to think is safe, Nachenberg said.
But unfortunately it isn’t. It has virus code hidden in its background that IE isn’t protecting you from. While you’re looking atsite,virus is downloaded onto your computer, he said. That’s one way of catchingnasty virus.
Duringpast two years, another prevalent way to catchvirus has been through downloads computer users share with one another, mostly on music sharing sites, Kuo said. On Limewire or Kazaa, for instance, teenagers or other music enthusiasts might think they’re downloading that latest Justin Timberlake song, when in reality they’re downloadingvirus straight into their computer. It’s easy forvirus writer to putdownload withvirus on one of these sites because everyone’s sharing with everyone else anyway.
Here’s one you might not have thought of. If you use Outlook or Outlook Express to send and receive email, do you havepreview pane below your list of emails that showscontents ofemail you have highlighted? If so, you may be putting yourself at risk.
Some viruses, thoughsmall percentage according to Nachenberg, are inserted straight into emails themselves.
Forget openingattachment. All you have to do is viewemail to potentially getvirus, Kuo added. For instance, have you ever opened or viewedemail that states it’s “loading”? Well, once everything is “loaded,”virus inemail might just load onto your computer.
So if I were you, I’d click on View ontoolbar in your Outlook or Outlook Express and closepreview pane. (You have to click on View and then Layout in Outlook Express.)
Onnetwork at work? You could getvirus 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 attackmachine itself rather than individual files.
Worms sit in your working memory, or RAM, Nachenberg said.
OK, so we’ve talked about howviruses get intocomputer. How do they cause so much damage once they’re there?
Let’s say you’ve caughtclassic virus, one that replicates and attacks various files on your computer. Let’s go back toexample ofvirus 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.
Oftendestructionvirus causes is pegged tocertain event or date and time, calledtrigger. For instance,virus could be programmed to lay dormant until January twoeight. 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, forvirus to cause your computer to be acting slow or in weird ways. And that leads us tonew segment –reason virus writers would want to waste their time creating viruses infirst place.
The majority of viruses are still written by teenagers looking for some notoriety, Nachenberg said. Butgrowing segment ofvirus-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 createvulnerability 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.). Oncevirus writer receivessignal, 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, fromnewsgroup. As inTrojan 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 toreal viruses. Let’s say we have Joe Shmo virus writer. He sends outvirus that ends up infectingthousand machines. But he doesn’t wantfeds on his case. So he instructsviruses onvarious machines to send their signals, not of course to his computer, but toplace that can’t be traced. Hotmail email happens to beexample of one such place, Kuo said.
OK, sovirus 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. Ifauthorities could track downoriginal senders of spam, they could crack down on spam itself. Spam senders don’t want that.
Ever heard of phishing emails? Those areones 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 sentsame way spam is sent, by sending them via innocent computers.
Of course makers of anti-virus software usevariety of methods to combatonslaught of viruses. Norton, for instance, uses signature scanning, Nachenberg said.
Signature scanning is similar toprocess 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 matchcode in it with similar code in your computer. When it finds such virus code, it lets you know!
©twozerozerofour by Kara Glover
Aboutauthor:
Kara Glover isComputer Tutor and Troubleshooter.
You can find her articles and tutorials on topics such as
Microsoft Word®, Excel®, and PowerPoint® on her website: http://www.karathecomputertutor.com
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