Computer Viruses

Module A04c

Audience and Objectives |About this document

What is a biological virus?
What is a computer virus?
What do viruses do?
Some computer viruses
Where do computer viruses come from?
What Do Computer Viruses Infect?

How do you "catch" a virus?
- Other sources of viruses
What this means to you
What Can You Do To Protect Yourself?
Some virus protection programs available
In the future...

In a Web browser, clicking these colored lines getsyou back to the Contents.

What is a biological virus?

Not a complete cell
A self-reproducing clump of genetic material
Viruses invade living cells
They force the living cells to produce more virus materials
They often prevent the cell from functioning normally,
causing considerable damage

What is a computer virus?

Not a complete program
Self-reproducing clump of program code
Viruses invade useful programs
They alter the program to produce more virus code
They often prevent programs from functioning normally,
and cause considerable damage

What do viruses do?

Phase One: Replication
Phase Two: Message
Phase Three: Mischief!

Phase One: Replication

Virus finds a program or file and inserts itself
This may be on another disk or on the same one

Phase Two: Message

After a certain time, most viruses deliver a message
They may replicate themselves a certain number of times...
or wait for a certain date

The message may be...
- A funny picture or joke
- A political slogan

Phase Three: Mischief!

Most common: erasing disks - especially hard disks!
Other forms of mischief are possible, too...

Some Computer Viruses...

Monkey: erases your disk
Michelangelo: Produces message and mischief on Michelangelo's birthday
Red Cross: Shows a picture of an ambulance going across the screen
Concept: demonstrates how a virus can infect a Microsoft Word document,but does no direct damage
Cookie Monster:
- Message: I WANT A COOKIE!
- Mischief: locks up the computer until you type FIG NEWTON

What Do Computer Viruses Infect?

Executable programs - that is, software that can be run. Examples:
- Word processors, like Word Perfect, Ami Pro, Microsoft Word
- Spreadsheet programs, like Lotus 1-2-3, Microsoft Excel
- Database programs, like FoxPro, Paradox, Approach, Access
- Integrated applications, like Claris Works, Microsoft Works
- Utility programs, like Norton Disk Doctor, Central Point PC Tools
Operating system programs - that is, the software that runs yourcomputer. Examples:
- DOS command.com and other parts of DOS
- Macintosh Finder and "inits"
- Parts of Windows 3.1 and Wndows 95
Parts of disks that carry technical information
- Boot records: tells the computer what to do when its starts up
- File Allocation Tables (FATs): tell the computer how the disk is organized
Data files with built-in programability ("macros")
- Microsoft Word document files
- Lotus and Excel spreadsheet files

How Do You "Catch" A Virus?

Like a real virus, you need contact
Computer labs are a "good" place for your disk to get sick!
(like kids going to school)
When you put your diskette in the drive, a virus on the hard disk may replicateitself on one of your files.

Other Sources Of Viruses...

Computer bulletin boards
Sharing disks with friends
On-line services (but these often take precautions)
Rarely: commercial programs
(disgruntled employees; accidental inclusion)

What This Means To You...

Be careful when you use public computer facilities
Viruses can really cause you a problem if you use computers frequently

What Can You Do To Protect Yourself?

Use virus checking programs when they are available in labs
Keep your diskette write-protected (hole open) if you don't intendto write anything on it (Program diskettes, master data files)
Get a copy of a virus checking program
Use it at home and at work
Update the program frequently: new viruses appear frequently

Virus Information

Virus information is available on the Web in several places. In additionto the anti-virus program developers listed just below, here are a coupleof authoritative places you can check The University of Michigan VirusBusters, "a group of Information Technology Division (ITD) staff membersat the University of Michigan (U-M) who are dedicated to assisting theU-M community with the control and prevention of computer viruses." Thishas good general information about virus protection, and also a sectionof hoaxes and scams. http://www.umich.edu/~wwwitd/virus-busters/

Some Virus Protection Programs Available

WCC uses Sophos anit-virus, but Sophos is intended for networked business and non-profit organizations. To find a good anti-virus program, check these sites that provide reviews:

The future...?

Virus attacks are on the increase
No letup is in sight
We must continually guard against attacks with virus detection programs.

Audience:

This module is for anyone who will be using a computer. It is helpful ifyou know a little very basic computer terminology, such as what is a disk?and what is a program?

Objectives

When you successfully complete this lesson, you will be able to...

Discuss the similarities between biological viruses and computer viruses
Explain the "life cycle" of a computer virus
Explain where computer viruses come from and how computers "catch" them
Discuss how to protect yourself from virus infection

About this document...

Module A04c: Computer Viruses

Review: A04cr
Author:: LaurenceJ. Krieg
Institution:: Departmentof Computer Information Systems, WashtenawCommunity College
Date:: Original 3 March 1995 (PowerPoint); Minor revision: 2010-01-14