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Extension Technology and
Computer Services


University of Missouri-Columbia   Extension Technology and Computer Services—ETCS

November 2002
  Vol. 19, No. 5

A Technology Newsletter for Extension Specialists



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Useful Information
by John Myers

While helping some users this past month with problems on their computers, I realized that the users wanted to learn more about the terms we use to describe events that take place on their computer. After explaining these events, the users would say "I wish someone would write this down for reference." The following paragraphs will explain what viruses, worms, Trojan horses, and hoaxes are and what tools we have to understand and combat them.

There are many different definitions of a computer virus. Most definitions state a virus is a program that can infect other programs or files. Until the infected program or file is processed on the computer, it can't do harm or spread itself. It requires "a user" to get it started. There are many different types of viruses; boot sector viruses, macro viruses, file viruses, logic bombs, and time bombs to name a few. Not all viruses are harmful, some just display messages on the screen or play little tricks, but there are some viruses that will delete files or reformat your hard drive.

Since a virus requires a user to get it started, there is time to find and clean viruses. This is what antivirus software does. When properly configured, antivirus software will scan a program or file before it is loaded into the computer's memory. If the software finds a virus it will either remove the virus or put the infected file in quarantine so it can't be spread. Viruses' main method of spread is by email and file transfer. Our email system has antivirus software running and scans all email messages for known viruses and removes any found in email. This prevents it from actually reaching your inbox. We also have antivirus software on our computers, but sometimes it gets turned off and then it doesn't get turned back on. There are a couple of things you can do to help protect yourself including leaving Norton Anti-virus enabled on your machine. Turn off the "Preview Pane" option in Outlook. If you get an email from someone you don't know that looks suspicious, don't read it! Delete it. If you get a cd or floppy from someone or have put your floppy in someone else's computer, scan it with the antivirus software before using it in your computer.

A worm is a virus that doesn't wait for someone to spread it around; it uses networks and the Internet to propagate itself. In English, this means worms are a more dangerous type of virus. They don't require a user to start them and they look for ways to propagate themselves. Worms look for file shares. When you create a file share, the default security permissions are set to allow everyone to access the file share. To protect yourself, you should restrict access to your file shares. If

you are running a Windows 9x operating system you should assign a password to your share. If you are running a Windows NT operating system (Windows 2000 or Windows XP) you should remove the "everyone" permission and assign rights to particular users or groups.

A Trojan horse is a program that appears to do one thing, but is actually doing malicious activities in the background. Technically, Trojans are not viruses since they do not replicate themselves, but Trojan horse programs can be just as destructive. Trojan horses can be used to reduce security on your computer to allow others to gain access.

Hoaxes are the best "virus" of all. Hoaxes are usually emails that turn YOU into the virus. The email scares you into thinking that you received a virus and instructs you to delete it. It will tell you what to search for and delete. The only problem is that the file it wants you to delete is not infected and is a vital operating system file. Depending on the file you delete, things can immediately start effecting the operation of your computer or wait and make it unbootable.

If you receive a message about a possible virus, first think before acting. Ask yourself, "Is this person an expert on computer viruses?" The answer is usually no. Find out about the virus yourself first and then act. For example, recently I have seen an old hoax about jdbgmgr.exe reappearing. I went to Norton's site ( and clicked on the "Search Virus Encyclopedia". In the search box I typed jdbgmgr.exe and then clicked on the search button. I was returned four hits that told me about this hoax. There are other web sites like that you can visit to find out if a virus is a hoax. If it's not a hoax then the sites will display useful information on how to remove the infection.



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