1. COMPUTER VIRUSES Class: Year 8 ‘A’ Date : 2 nd February 2009

2. 2 Lesson Content What is computer virus ? What does virus do? What is computer worm? How does computer virus works? How are viruses spread? How can they be prevented? The computer Misuse Act. 2

3. 3 What is computer virus ? is a piece of software or programming code. a computer virus makes copies of itself. (they pass from one computer to another like a real life biological virus) 3

4. 4 What does virus do? Intentionally tiny program created to destroy data / program Can be dangerous – loss of data, cripple the system unit Designed to cause harm Damages depends on types of viruses 4

5. 5 Some damages – caused computer system out of action: ~ crashing memory ~ erasing files ~ corrupting data What does virus do? 5

6. 6 Types of computer viruses: I love you, Michelangelo 6

7. 7 Virus is made up of TWO parts: ~ The infector – is part on a virus program ….copies the whole virus from an infected computer into a disk/another computer through a network 7

8. 8 ~ The detonater – is a part on a virus program ….will perform the intended nasty work. 8

9. 9 Typical effects of “Detonaters” System cannot be booted Funny messages appear on screen Characters falling from bottom of the screen Part of/all data on the disk is deleted Files are renamed so user cannot recall them System performance is slow Hardware malfunction System hang up RAM memory size becomes smaller even the isn’t a lot of programs. 9

10. 10 What is computer worm ? Does not alter programs/data Reproduces itself rapidly…using up all available storage space…hence no space for user to store new programs/data Lead to system slowdown/total system failure Example: Melissa 10

11. 11 Difference between virus & worm? VIRUS ~ a program that can reproduced itself ~ cause harm to files/other programs on the same computer WORM ~ a type of virus ~ does not alter….reproduces itself….system slowdown ~ spreads from one computer to another by network 11

12. 12 How does computer virus works? 12

13. 13 How are viruses spread? They can be downloaded from some web pages. If a webpage is offering free games or ringtones to download and it seems too good to be true – it probably is. If you download the file, there might be a virus hidden inside it. 13

14. 14 How are viruses spread? They can be caught from opening attachments or clicking on links in emails. If you get an email from someone you don’t know, don’t ever click on a link in the mail and don’t open any attachments. 14

15. 15 If someone has a virus on their computer and they save a file onto a floppy disk or USB stick, the virus might also be saved onto the media. If you borrow your friend’s USB stick and it has a virus on it, you could transfer it to your computer. How are viruses spread? 15

16. 16 How can they be prevented? 16

17. 17 How can they be prevented? Make sure that you have anti-virus software on your computer. Get the anti-virus software to scan your hard disk. If a virus is found, the software will either remove it or quarantine it. Example: PC Cillin, Norton Anti-virus, AVG, Avast. 17

18. 18 How can they be prevented? Do not allow unauthorized people to use Do not use pirated software Do not share software with unknown sources Do not copy software/data from unknown sources Back up system frequently Consult teacher/parents before installing new software 18

19. 19 Dangers of internet Trojan Horse ~ a program ~ secretly performs other undesirable functions Spy ware functions – spy on your information Backdoor functions – makes your computer to be remotely controlled 19

20. 20 Why should you update? Because new viruses are being written every single day, your anti-virus software soon gets out of date. It might not recognise new viruses or know what to do with them. 20

21. 21 The computer Misuse Act (1990) It is illegal to obtain unauthorized access / modify its content. Computer crime: Accessing computer material without permission…stealing Accessing computer material without permission intent to commit criminal offences…hacking Altering computer material without permission….destroy someone else’s data 21

22. 22 How do you update? You should update your anti-virus software at least once a week. This is free to do, just go to the software’s main website and download any patches 22

23. 23 The End…. Q & A 23