1. COMPUTER VIRUSES
Computer Technology

2. Computer Virus A kind of malicious software written intentionally to
enter a computer without the user’s permission or knowledge,
with the ability to replicate itself, thus continuing to spread.

3. What does a virus do? Deletes files, destroys data Corrupts files
Corrupts your computer system
Displays irritating messages
These days, many viruses are more interested in harvesting information from your computer to be used for illegal purposes

4. Viruses Spread Themselves
It’s like spreading a virus in the human population – we get sick when we are exposed to a virus and our defenses are down
Your computer gets exposed to a virus when its defenses are down

5. Spreading Viruses
Viruses spread because people distribute infected files by exchanging disks and CDs, sending attachments, and downloading documents from the Internet.
When you open the infected file, the virus may open and waits to infect the next program you run or disk you use

6. Spreading Viruses (continued)
Viruses have the ability to lurk in a computer for days or months, quietly replicating themselves
You may not even know your computer has a virus, thus making it easier to spread the virus

7. Trigger Events
An event that activates a task often associated with a computer virus
Time Bomb
Watches for the PC clock to reach a certain date to activate the virus
Example
Michelangelo virus
Damages files on March 6 the artist’s birthday
Logic Bomb
Watches for a specific set of input to activate the virus

8. Classification of Viruses

9. Malware Malicious software
Intended to damage computers or disrupt computer systems

10. Adware
Automatically displays advertisements in order to generate revenue

11. Spyware
Software that enables the user to gain information from a computer without the user’s knowledge

12. File Virus
Virus that infects programs or executable files. When the program is run, the virus is activated.
Example
Chernobyl
Notorious for overwriting a section of the hard disk, making it impossible to access data

13. Boot Sector Virus
Infects the system files that your computer uses every time it is turned on
Cause widespread damage and recurring problems
Example
Stoned Virus
Every time you turn on your computer the virus is activated and infects any non-write-protected files including your hard disk

14. Trojan Horse
Computer program that seems to perform one function while actually doing something else
Different from a virus because it does not make copies of itself
Makes your computer susceptible to malicious intruders
Different tasks that can be affected
Stealing passwords
Deleting files

15. Trojan Horse Example

16. Worm
Software program designed to enter a computer system usually through a network, through security holes and then replicate itself
Spreads from computer to computer by copying and multiplying itself thus spreading throughout a network

17. Worm Example

18. Protecting Yourself from Viruses
Antivirus software
Software that attempts to recognize and destroy viruses before they infect your computer

19. Protecting Yourself from Viruses
Updating
Keep your programs updated. Companies often provide updates to fix vulnerabilities.

20. Protecting Yourself from Viruses
Don’t open any suspicious s, attachments, or ads.
Be careful what you download from the internet.

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