COMPUTER VIRUSESCOMPUTER VIRUSES

Computer TechnologyComputer Technology

Computer VirusComputer Virus

Set of program instructions Set of program instructions that attaches itself to a file, that attaches itself to a file, reproduces itself, and/or reproduces itself, and/or spreads to other filesspreads to other files

It canIt can• Corrupt filesCorrupt files• Destroy dataDestroy data• Display irritating Display irritating

messagesmessages• Corrupt computer Corrupt computer

systemssystems

Spreading VirusesSpreading Viruses Viruses spread because people distribute infected Viruses spread because people distribute infected

files by exchanging disks and CDs, sending e-mail files by exchanging disks and CDs, sending e-mail attachments, and downloading documents from attachments, and downloading documents from the Internet.the Internet.

Viruses attach themselves to files with .exe, .com, Viruses attach themselves to files with .exe, .com, or .vbs filename extensionsor .vbs filename extensions

When you open the infected file, the virus opens When you open the infected file, the virus opens and waits to infect the next program you run or and waits to infect the next program you run or disk you usedisk you use

Spreading Viruses (continued)Spreading Viruses (continued) Viruses have the ability to lurk in a Viruses have the ability to lurk in a

computer for days or months, quietly computer for days or months, quietly replicating themselvesreplicating themselves

You may not even know your You may not even know your computer has a virus, thus making it computer has a virus, thus making it easier to spread the viruseasier to spread the virus

Trigger EventsTrigger Events An event that activates a task often An event that activates a task often

associated with a computer virusassociated with a computer virus Time BombTime Bomb

• Watches for the PC clock to reach a certain Watches for the PC clock to reach a certain date to activate the virusdate to activate the virus

ExampleExample• Michelangelo virusMichelangelo virus

Damages files on March 6 the artist’s birthdayDamages files on March 6 the artist’s birthday Logic BombLogic Bomb

• Watches for a specific set of input to activate Watches for a specific set of input to activate the virusthe virus

Classification of VirusesClassification of Viruses

File VirusFile Virus Virus that attaches to an application Virus that attaches to an application

programprogram• ExampleExample

ChernobylChernobyl• Notorious for overwriting a section of the hard Notorious for overwriting a section of the hard

disk, making it impossible to access datadisk, making it impossible to access data

Boot Sector VirusBoot Sector Virus Infects the system files that your Infects the system files that your

computer uses every time it is turned computer uses every time it is turned onon

Cause widespread damage and Cause widespread damage and recurring problemsrecurring problems• ExampleExample

Stoned VirusStoned Virus• Every time you turn on your computer the virus is Every time you turn on your computer the virus is

activated and infects any non-write-protected files activated and infects any non-write-protected files including your hard diskincluding your hard disk

Macro VirusMacro Virus MacroMacro

• A miniature program that usually A miniature program that usually contains legitimate instructions to contains legitimate instructions to automate a document or taskautomate a document or task

This virus infects a macroThis virus infects a macro• ExampleExample

Melissa VirusMelissa Virus• Attaches itself to Microsoft Word documentsAttaches itself to Microsoft Word documents

Codemas VirusCodemas Virus• Attaches itself to Microsoft Excel spreadsheetsAttaches itself to Microsoft Excel spreadsheets

Other VirusesOther Viruses

Trojan HorseTrojan Horse Computer program that seems to Computer program that seems to

perform one function while actually perform one function while actually doing something elsedoing something else• Different from a virus because it does Different from a virus because it does

not make copies of itselfnot make copies of itself Different tasks that can be affectedDifferent tasks that can be affected

• Stealing passwordsStealing passwords• Deleting filesDeleting files

Trojan Horse ExampleTrojan Horse Example

WormWorm Software program designed to enter Software program designed to enter

a computer system usually through a a computer system usually through a network, through security holes and network, through security holes and then replicate itselfthen replicate itself

Spreads from computer to computerSpreads from computer to computer

Worm ExampleWorm Example

Protecting yourself from virusesProtecting yourself from viruses Antivirus software Antivirus software

• Set of utility programs that looks for and Set of utility programs that looks for and eradicates a wide spectrum of problems, eradicates a wide spectrum of problems, including viruses, Trojan horses, and including viruses, Trojan horses, and wormsworms

• ExampleExample McAfee Virus ScanMcAfee Virus Scan

Don’t open e-mails attachments that Don’t open e-mails attachments that have strange names or are from have strange names or are from people you don’t recognizepeople you don’t recognize

ResourceResource

Parsons, June Jamrich, and Dan Oja. Parsons, June Jamrich, and Dan Oja. Computer ConceptsComputer Concepts. Boston: Course . Boston: Course Technology - Thompson Learning, Technology - Thompson Learning, 2002. 2002.