A computer virus is a program designed to replicate and spread on its own, without a user's knowledge. Computer viruses spread by attaching themselves to another program, such as word processing or spreadsheet programs (usually macro viruses) or to the boot sector of a diskette. When an infected file is run or opened, or the computer is started from an infected disk, the virus itself is executed. Often, it stays in memory, waiting to infect the next program that is run or the next disk that is accessed. Many viruses perform trigger events; for example, they might display a message on a certain date or delete files after the infected program is run a certain number of times. While some of these trigger events are benign, others can be very costly and cause significant damage.

Infected E-mail attachments are the biggest source of macro viruses. At Mount Allison, this most commonly occurs with Microsoft Word documents.

Boot sector viruses are most often spread via diskette. Once infected, your computer may infect every diskette put in your floppy disk drive, as well as erasing or damaging files on your computer. You can very easily be a source of infection without knowing it.

As the name implies, a Trojan Horse program comes with a hidden surprise intended by the programmer but totally unexpected by the user. A Trojan Horse is often designed to cause damage or do something malicious to a system, but is disguised as something useful or harmless (such as a "joke" program. Unlike viruses, Trojan Horses don't make copies of themselves. Like viruses, they can cause significant damage to a computer. There are many Trojan Horses that allow an attacker to control your computer over the Internet - allowing the attacker to read or change your files, or make your computer "crash".

Worms are like viruses in that they do replicate themselves. However, instead of spreading from file to file, they spread from computer to computer, infecting an entire system. Worms most often cause damage by overwhelming computers and networks with thousands of copies of the worm.

Although they are not truly viruses, a general discussion of computer viruses is often assumed to include Trojan Horses and Worms.

As with real viruses, it is impossible to guarantee that you won't become "infected", but you can reduce the risk.

1. Back up your data often, in several places if possible.
2. Be wary of opening e-mail attachments or files of unknown or suspicious origin, especially ".EXE" files. If someone you don't know sends you an e-mail attachment, you probably don't need to open it - why would someone you don't know be sending it to you?
3. Use an up to date virus scanning software package. This includes keeping the virus "signatures" up to date so the program can detect new viruses.

All University-owned machines with a standard Computing Services configuration have Trend Micro OfficeScan installed. It is configured to do "on access" scanning which means that all files are scanned before they are used. It is also configured to automatically update the .DAT (virus signature) files each time the machine is started.

In addition, all e-mail from off-campus addressed to an "mta.ca" address is scanned for viruses automatically. If the message contains a virus, the sender is notified and the message is not delivered to you. We also block any email messages with attachments of the following type: exe, scr, bat, pif, com and zip. The sender is also notified when these types of messages are blocked.

Software is available for faculty and staff under the agreement between Kaspersky and the NB/PEI ECN, of which Mount Allison is a member. For more information, go to https://www.mta.ca/virusscan.

PC-cilin antivirus software is no longer available free of charge for students and staff members. Please Note: If you have Trend Micro PC-Cillin installed on a home machine with a Mount Allison license, it must be removed by the end of October 2010, when the license expires.

For free anti-virus software, students can check out AVG or Avast.

Virus Myths

F-Secure Hoax Description Database