• Virus - A computer virus is a small program written to alter the way a computer operates, without the permission or knowledge of the user. A virus must meet two criteria:
  1. It must execute itself. It will often place its own code in the path of execution of another program.

  2. It must replicate itself. For example, it may replace other executable files with a copy of the virus infected file. Viruses can infect desktop computers and network servers alike. Some viruses are programmed to damage the computer by damaging programs, deleting files, or reformatting the hard disk. Others are not designed to do any damage, but simply to replicate themselves and make their presence known by presenting text, video, and audio messages. Even these benign viruses can create problems for the computer user. They typically take up computer memory used by legitimate programs. As a result, they often cause erratic behavior and can result in system crashes. In addition, many viruses are bug-ridden, and these bugs may lead to system crashes and data loss.

• Trojan Horse - A Trojan Horse is a program that appears to be something it is not. Typically a Trojan Horse will perform a function beneficial to the user while at the same time doing a destructive operation in the background. The major difference between a Trojan Horse and a Virus is the fact that the Trojan Horse does not replicate itself.

• Worm - Worms are programs that replicate themselves from system to system without the use of a host file. This is in contrast to viruses, which requires the spreading of an infected host file. Although worms generally exist inside other files (often Word or Excel documents,) there is a difference between how worms and viruses use the host file. Usually the worm will release a document that already has the "worm" macro inside the document. The entire document will travel from computer to computer, so the entire document should be considered the worm.

• Virus Hoax - A virus hoax is a false warning about a computer virus. Typically, the warning arrives in an e-mail message. These messages are usually forwarded using distribution lists and they will typically suggest that the recipient forward the note to other distribution lists. To learn more about hoaxes visit CIAC Hoaxbusters or vmyths.com. As a general rule, never forward a e-mail that tells you should forward the message to everyone you know; it's almost certainly a hoax.

In order to prevent viruses, Trojan horses, and worms from infecting your computer, Coastal recommends that you install anti-virus software and keep it updated. There are a variety of anti-virus packages available on the market today. Some of the more well known commercial packages include Norton Antivirus, McAfee Virus Scan and TrendMicro. In addition to the various commercial products there are several free anti-virus packages available including, AVG and VCatch.*

*While Coastal recommends that users install and update anti-virus software, Coastal does not recommend nor support any particular anti-virus software.