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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 send a brief message to let me know where it appeared: kara333@earthlink.net

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URL: http://www.karathecomputertutor.com
Author photo: http://www.karathecomputertutor.com
Date of copyright: November 2004

All About Computer Viruses
by Kara Glover
kara333@earthlink.net

Your computer is as slow as molasses. Your mouse freezes every 15 minutes, and that Microsoft Word program just won�t seem to open.

You might have a virus.

Just what exactly is a virus? 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. But the code 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, a research fellow with McAfee AVERT, a research arm of anti-virus software-maker McAfee Inc.

In this article, though, we�re not talking about the good guys, or the agents. We�ll be talking about the bad guys, the viruses.

A long, long time ago in computer years, like five, most viruses were comprised of a similar breed. They entered your computer perhaps through an email attachment or a floppy disk (remember those?). Then they attached themselves to one of your files, say your Microsoft Word program.

When you opened your Microsoft Word program, the virus replicated and attached itself to other files. These could be other random files on your hard drive, the files furthest away from your Microsoft Word program, or other files, depending on how the virus writer wanted the virus to behave.

This virus code could contain hundreds or thousands of instructions. When it replicates it inserts those instructions, into the files it infects, said Carey Nachenberg, Chief Architect at Symantec Research Labs, an arm of anti-virus software-maker Symantec. Corp.

Because so many other types of viruses exist now, the kind just described is called a classic virus. Classic viruses still exist but they�re not quite as prevalent as they used to be. (Perhaps we could put classic viruses on the shelf with Hemingway and Dickens.)

These days, in the modern era, viruses are known to spread through vulnerabilities in web browsers, files shared over the internet, emails themselves, and computer networks.

As far as web browsers are concerned, Microsoft�s Internet Explorer takes most of the heat 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 to a website 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 at the site, the virus is downloaded onto your computer, he said. That�s one way of catching a nasty virus.

During the past two years, another prevalent way to catch a virus 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 downloading a virus straight into their computer. It�s easy for a virus writer to put a download with a virus 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 have a preview pane below your list of emails that shows the contents of the email you have highlighted? If so, you may be putting yourself at risk.

Some viruses, though a small percentage according to Nachenberg, are inserted straight into emails themselves.

Forget opening the attachment. All you have to do is view the email to potentially get a virus, Kuo added. For instance, have you ever opened or viewed an email that states it�s �loading�? Well, once everything is �loaded,� a virus in the email might just load onto your computer.

So if I were you, I�d click on View on the toolbar in your Outlook or Outlook Express and close the 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, the classic viruses, they attack the machine itself rather than individual files.

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

OK, so we�ve talked about how the 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 the example of the 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 the 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 � the reason virus writers would want to waste their time creating viruses in the first place.

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

For these other intentions, we first need to explain the �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 the virus writer receives the 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 the 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 the 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 the feds on his case. So he instructs the viruses on the 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 the 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 the authorities could track down the original senders of spam, they could crack down on spam itself. Spam senders don�t want that.

Ever heard of phishing emails? Those are the 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 the 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 the onslaught of viruses. Norton, for instance, uses signature scanning, Nachenberg said.

Signature scanning is similar to the 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 the code in it with similar code in your computer. When it finds such virus code, it lets you know!

�2004 by Kara Glover

About the author:
Kara Glover is a Computer Tutor and Troubleshooter.
You can find her articles and tutorials on topics such as
Microsoft Word�, Excel�, and PowerPoint� on her website:

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Winning the War On Spam

For years I didn't worry much about spam.

But lately it's got out of control. Over half of my email is now spam, and it was growing by the week - until I took action.

This article shows you some strategies for winning the war on spam.

------------------------------------------------

How Do They Get Your Address?

------------------------------------------------

In the old days, spammers got their addresses mainly from Newsgroups - if you didn't post to Newsgroups, you were reasonably safe. But they're now using a much more efficient method to build their lists - email harvesters.

Email harvesters are robots that roam the Internet collecting email addresses from web pages. Examples are EmailSiphon, Cherry Picker, Web Weasel, Web Bandit and Email Wolf, to name just a few.

How can you protect yourself from email harvesters?

By 'munging' (mung = 'mash until no good') or cloaking your email address.

There are many ways of munging your address - the easiest technique is to use ASCII code for the punctuation in your email address (instead of symbols).

For the colon after mailto use : and for the @ symbol use @ and for the period use . . With this method, your email address would become:

mailto:yourname@yourdomain.com

but it will display as:

mailto:yourname@yourdomain.com

Your email address will appear exactly as it did before, and it will still be 'clickable', but email harvesters will ignore it and move on.

There are also JavaScript's that you can insert into your web page that will make your email address visible to humans but invisible to harvesting programs. Here's one that works very well: http://pointlessprocess.com/JavaScripts/anti-spam.htm

-----------------------------

How To Fight Spam

-----------------------------

The most important thing is never, ever, reply to spam.

Most spam contains an innocent-looking 'remove me' email address. Do not use it. Here's why:

Spammers typically buy a CD containing a million or so email addresses, but they have no idea how many of those addresses are active. So before beginning their marketing campaign in earnest, they send out a 'test message' to the entire list.

The test message contains an email address for removing yourself. When you reply to that address, it confirms to the spammer that your address is active and therefore worth spamming.

Worse still, the spammer may be distilling from that CD a list of confirmed active addresses that he will then sell to another spammer.

The key to dealing with spam is to report it to a 3rd party: (1) the affiliate program that the spammer is advertising, (2) the spammer's web host, or (3) the ISP the spammer used to connect to the Internet.

When you report spam to a 3rd party, remember to be polite - they didn't send the spam and they're probably just as anti-spam as you are.

(1) Reporting to Affiliate Programs

Many spammers are affiliates advertising someone else's products or services. So look for a website address that contains an affiliate link, something like this: www.affiliateprogramdomain/841526

Then just send an email to the affiliate program (abuse@affiliateprogramdomain.com), informing them that you are receiving spam from one of their affiliates.

Most affiliate programs have zero tolerance for spamming and will remove an affiliate spammer without warning.

Now, affiliate spammers don't want you to see their affiliate link, so many of them send their email as HTML. All you see in the message are the words 'Click Here and Order Now'.

But in your browser just click on 'View Source Code' and search for the letters 'http'. That will take you to the spammer's affiliate link.

(2) Reporting to Web Hosts

If the spam doesn't contain an affiliate link, it's likely that it is coming from the owner of the domain name. In that case you'll have to report it to the spammer's web host or their ISP.

To make a report to the spammer's web host just go to Whois, the directory of registered domain names: http://www.netsol.com/cgi-bin/whois/whois

Type in the spammer's domain (the website address that appears in the spam) together with the extension (.com, .org, .net etc).

The host for that domain will usually be listed as the Technical Contact in the Whois record and there will be an email address for contacting them.

(3) Reporting to ISPs

To report a spammer to his Internet Service Provider, you'll have to look at the spam's 'extended headers'.

Extended headers show the servers that the message passed through in order to get to you. The instructions for viewing extended headers will vary depending on what email client you are using.

=> In Pegasus Mail, open the offending message and then

right-click and choose 'Show raw message data'.

=> In Eudora Light, click on 'Tools' in the top menu

bar, and then 'Options', and then select the

checkbox option that says 'Show all headers (even

the ugly ones)' and click OK.

=> In Outlook Express, open the offending message,

select 'Properties' from the File menu and then

click the 'Details' tab.

Reading and understanding extended headers is quite a detailed subject. Here's an excellent free tutorial on how to decipher extended headers: http://www.doughnut.demon.co.uk/SpamTracking101.html

As an alternative to these reporting techniques, you could use a web-based spam reporting service such as SpamCop (www.spamcop.net). SpamCop deciphers the spam's message headers and traces the mail back to its source.

Wishing you every success in the fight against spam!

------------------------------------------------------------
Michael Southon has been writing for the Internet for over 3
years. He has shown hundreds of webmasters how to use this
simple technique to build a successful online business. Click
here to find out more: http://ezine-writer.com/
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Winning the War On Spam