VIRUSES and MALWARE

Computer Technology Notes 5

Computer VirusO A virus is a set of

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

O It canO Corrupt filesO Destroy dataO Display irritating messagesO Corrupt computer systems

Spreading VirusesO Just like a human virus, computer viruses

can only spread by contact with an infected computer. Ways they are spread:O Infected files on portable storage devices are

spread from computer to computerO Opening infected e-mail attachmentsO Downloading infected documents or programs

from the InternetO When you open the infected file, the

virus opens and waits to infect the next program you run or storage device you use

Spreading Viruses (continued)

O Viruses have the ability to lurk in a computer for days or months, quietly replicating themselves

O You may not even know your computer has a virus until it is too late, thus making it easier to spread the virus

Trigger Events

O An event that activates a task often associated with a computer virus

O Time BombO Watches for the PC clock to reach a certain date to activate the virus

O ExampleO Michelangelo virus

O Damages files on March 6, the artist’s birthdayO Logic Bomb

O Watches for a specific set of input to activate the virus

Classification of Viruses

File VirusO Virus that attaches to an application

programO Example

O ChernobylO Notorious for overwriting a section of the

hard disk, making it impossible to access data

Boot Sector VirusO Infects the system files that your

computer uses every time it is turned on

O Cause widespread damage and recurring problemsO Example

O Stoned VirusO Every time you turn on your computer the

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

Macro VirusO Macro

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

O This virus infects a Word or Excel DocumentO Example

O Melissa VirusO Attaches itself to Microsoft Word

documentsO Codemas Virus

O Attaches itself to Microsoft Excel spreadsheets

Other Malware (Malicious Software)

Trojan HorseO Computer program that seems to

perform one function while actually doing something elseO Different from a virus because it does

not make copies of itselfO Different tasks that can be affected

O Stealing passwordsO Deleting files

Trojan Horse Example

Worm

O Software program designed to enter a computer system usually through a network, through security holes and then replicate itself

O Spreads from computer to computer, often through your e-mail address list

Worm Example

Adware and SpywareO Adware appears as a pop-up

advertisement on a website on the Internet

O Some adware comes with spyware:O Spyware collects pieces of

information about you without your knowledge

O It can change computer settingsO It can slow down your computer

speedO It can change your home page or

make you lose your Internet connection

Protecting Yourself From Viruses and Other MalwareO Install antivirus software

O Antivirus software is a set of utility programs that looks for and eradicates a wide spectrum of problems, including viruses, Trojan horses, and worms

O ExamplesO McAfeeO Norton

Protecting YourselfO E-Mail

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

O Anti-spyware programsO Use especially for Windows-run

computersO Mac computers aren’t as vulnerable