Understanding Computer Viruses

What is a Virus?
A computer virus is one of thousands of programs that can invade computer systems (both IBM PC and Macintosh) and perform a variety of functions ranging from annoying (e.g., popping up messages as a joke) to dangerous (e.g., deleting files or destroying your hard disk). Trojan horses or worms are specific types of clandestine programs (loosely categorized as viruses) and can be just as dangerous. For simplicity’s sake, future mention of viruses in this document will refer to viruses, Trojan horses, and worms taken as a whole.

How Do Viruses Spread?
Computer viruses are programs that must be triggered or somehow executed before they can infect your computer system and spread to others. Examples include opening a document infected with a “macro virus,” booting with a diskette infected with a “boot sector” virus, or double-clicking on an infected program file. Viruses can then be spread by sharing infected files on a diskette, network drive, or other media, by exchanging infected files over the Internet via e-mail attachments, or by downloading questionable files from the Internet.

In a network environment, the most likely first entrance of a virus into the network will be through the group ware Internet Gateway. From there, it is easy for the viruses to spread to mail servers, file servers, workstations and laptops which are connected to the network.

How Can You Protect Yourself?
With dangerous viruses on the network, what can computer users do to protect their systems? Here are just a few hints:
•Be sure to install an anti-virus software program to guard against virus attacks on the servers and also the workstations in the network. Also, be sure you turn on the scanning features. It can’t protect you if it’s not enabled.
•Practice caution when working with files from unknown or questionable sources.
•Do not open e-mail attachments if you do not recognize the sender (though you may also receive viruses from people you know). Scan the attachments with anti-virus software before opening them.
•Download files only from reputable Internet sites, and be wary when exchanging diskettes or other media with friends.
•Scan your hard drive for viruses monthly. Even with these precautions, new viruses may find ways to enter your computer system.

Diagnosing a Virus Infection
How do you know if your computer has been infected with a virus? In short, if it starts acting funny - doing anything it didn’t do before- then a probable cause is some sort of computer virus. Here are some symptoms to watch for:
•Programs quit working or freeze up.
•Documents become inaccessible.
•Computer freezes up or won’t start properly.
•The CAPS LOCK key quits working—or works intermittently.
•Files increase in size.
•Frequent error messages appear onscreen.
•Strange messages or pictures appear onscreen.
•Your PC emits strange sounds.
•Friends and colleagues inform you that they’ve received strange e-mails from you, that you don’t remember sending.