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

• 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

Where Do Computer Viruses Come From?

• Clever programmers invent them
• Why would anyone create a virus? ...

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

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Some Virus Protection Programs Available

• McAfee (WCC uses this on all its Windows-based computers), fromNetwork Associates, Inc. (NAI): http://www.nai.com/default_mcafee.asp
• Data Fellows Data Fellows is a software development company whosemajor business areas are anti-virus, data security and cryptography softwareand groupware products. Check out their virus news at http://www.datafellows.com/vir-info/or their comprehensive list of hoaxes at http://www.datafellows.com/news/hoax.htm.
• Symantec, purveyors of Norton Utilities and other software, sponsoran antivirus research center (SARC), on the Web at http://www.symantec.com/avcenter/index.html.

The future...?

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

Audience:

Objectives

• 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)

Latest revision: Wednesday, 07-Nov-2001 13:02:32 EST