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  1. 1. Computer Virus 06/10/09
  2. 2. What is a Computer Virus <ul><li>A kind of software programs </li></ul><ul><ul><li>produced by unknown people and harmful to the computers </li></ul></ul><ul><li>Some varieties of these software are the </li></ul><ul><ul><li>Viruses , Worms and Trojan horses </li></ul></ul>06/10/09
  3. 3. What is a Computer Virus <ul><li>The term “Virus&quot; is often used in common </li></ul><ul><ul><li>to describe all kinds of malware (malicious software) </li></ul></ul>06/10/09
  4. 4. Damages done by Viruses <ul><li>Sometimes display unwanted messages </li></ul><ul><li>Some tend to destroy programs or data </li></ul><ul><li>Clog computer memory and hence sometimes result in system crashes </li></ul><ul><li>Format hard disks, Damage programs, Delete files </li></ul>06/10/09 Viruses
  5. 5. Damages done by Viruses <ul><li>Simply replicate themselves </li></ul><ul><li>Presents text, video, or audio messages making the user know their presence </li></ul><ul><li>Bug-ridden, and these bugs may lead to system crashes and data loss </li></ul>06/10/09
  6. 6. Virus spreading methods <ul><li>A viruses can copy itself and infect a computer </li></ul><ul><ul><li>without permission or knowledge of the user </li></ul></ul><ul><li>attaches itself to other software programs or data files </li></ul>06/10/09
  7. 7. Virus spreading methods <ul><li>Spreads from computer to computer when the host is taken to the uninfected computer </li></ul><ul><ul><li>over a network such as over the Internet or carrying it on a removable medium - a floppy disk, CD, or USB drive </li></ul></ul>06/10/09
  8. 8. Virus spreading methods <ul><li>Many viruses are existed in the Internet today and new ones are discovered every day. </li></ul><ul><ul><li>spread via downloaded software and data files, and email attachments, etc </li></ul></ul>06/10/09
  9. 9. Virus spreading methods <ul><li>Some old viruses are installed themselves into the disk boot sector </li></ul><ul><ul><li>runs when the user boot the computer from the disk </li></ul></ul>06/10/09
  10. 10. Virus spreading methods <ul><li>Some viruses spread through instant messaging </li></ul><ul><ul><li>A virus, in an infected machine, may send a web-address-link as a message to other contacting machines </li></ul></ul><ul><ul><li>Thinking the link is from a friend (a trusted source), the recipient may sometimes follow the link to the websit. </li></ul></ul>06/10/09
  11. 11. How Viruses are borne <ul><li>Unlike biological viruses, computer viruses do not simply evolve by themselves </li></ul><ul><ul><li>deliberately created by programmers, or by people who use virus creation software </li></ul></ul>06/10/09
  12. 12. How Viruses are borne <ul><li>Viruses are written as </li></ul><ul><ul><li>research projects, pranks, vandalism, </li></ul></ul><ul><ul><li>to attack the products of specific companies, </li></ul></ul><ul><ul><li>to distribute political messages, </li></ul></ul><ul><ul><li>and financial gain from identity theft, </li></ul></ul><ul><ul><li>spyware, and cryptoviral extortion . </li></ul></ul>06/10/09
  13. 13. How Viruses are borne <ul><li>Some virus writers </li></ul><ul><ul><li>consider their creations to be works of art </li></ul></ul><ul><ul><li>See virus writing as a creative hobby </li></ul></ul>06/10/09 Releasing computer viruses is a crime in most jurisdictions
  14. 14. Viruses can avoid detection <ul><li>To avoid detection by users, viruses employ different deception methods </li></ul><ul><ul><li>They do not make themselves to </li></ul></ul><ul><ul><ul><li>change the date of last modified </li></ul></ul></ul><ul><ul><ul><li>increase file sizes </li></ul></ul></ul><ul><ul><ul><li>damage the files </li></ul></ul></ul>06/10/09
  15. 15. Viruses can avoid detection <ul><ul><li>They kill the tasks associated with antivirus software before it can detect them </li></ul></ul>06/10/09
  16. 16. How Antivirus software works? <ul><li>Detect using a list of virus signature definitions </li></ul><ul><ul><li>comparing the files stored on fixed or removable drives (hard drives, floppy drives), against a database of known virus &quot;signatures&quot;. </li></ul></ul>06/10/09
  17. 17. How Antivirus software works? <ul><li>Use a heuristic algorithm to find viruses based on common behaviors </li></ul><ul><ul><li>Examin the content heuristics of the computer's memory (its RAM, and boot sectors) </li></ul></ul>06/10/09
  18. 18. How Antivirus software works? <ul><li>Some anti-virus programs gives you a real time protection </li></ul><ul><ul><li>Examin files as they are being opened, downloaded, copied, accessed, and transmitted etc </li></ul></ul>06/10/09
  19. 19. How Antivirus software works? <ul><li>They need regular updates </li></ul><ul><ul><li>in order to gain knowledge about the latest threats </li></ul></ul>06/10/09
  20. 20. Damage prevention & data recovering <ul><li>Take regular backups (including OS) on different media, unconnected to the system (most of the time) </li></ul>06/10/09 How to prevent damages caused by viruses?
  21. 21. Damage prevention & data recovering <ul><li>Use backups on optical media like CD and DVD (read-only), as they can no longer be affected by viruses. </li></ul><ul><li>Use an OS on a bootable, to start the computer if the installed OS become unusable. </li></ul>06/10/09 How to prevent damages caused by viruses?
  22. 22. Keep your computer Virus free <ul><li>Install reliable anti-virus software </li></ul><ul><ul><li>the most important step you can take towards keeping your computer clean of viruses </li></ul></ul><ul><li>Update your anti-virus software regularly </li></ul><ul><ul><li>variations of viruses and new ones can be slipped if your software is not current </li></ul></ul>06/10/09
  23. 23. Keep your computer Virus free <ul><li>Get immediate protection </li></ul><ul><ul><li>Configure your anti-virus software to boot automatically on start-up and run at all times </li></ul></ul>06/10/09
  24. 24. Keep your computer Virus free <ul><li>Don't automatically open attachments </li></ul><ul><ul><li>ensure that you examine and scan email and other attachments before they run as they might contain viruses </li></ul></ul><ul><li>Scan all incoming email attachments </li></ul><ul><ul><li>Do not open any email attached files if the subject line is questionable, unexpected or the source (address) is unknown, suspicious or untrustworthy </li></ul></ul>06/10/09
  25. 25. Keep your computer Virus free <ul><li>Delete chain emails and junk email </li></ul><ul><ul><li>Do not forward or reply to any of them, they clogs up the network </li></ul></ul><ul><ul><li>Some viruses can replicate themselves and spread through email as a chain </li></ul></ul>06/10/09
  26. 26. Keep your computer Virus free <ul><li>Be careful when downloading files from the Internet </li></ul><ul><ul><li>Ensure that the source is a legitimate and reputable one </li></ul></ul><ul><ul><li>save all downloads to one folder and test them with your own anti-virus software before use </li></ul></ul>06/10/09
  27. 27. Keep your computer Virus free <ul><li>Always scan new files for viruses before you use them </li></ul>06/10/09
  28. 28. Keep your computer Virus free <ul><li>Backup your files on a regular basis </li></ul>06/10/09
  29. 29. Keep your computer Virus free <ul><li>If your computer is on a network, make sure you have security steps in place to prevent unauthorized users putting files on your computer </li></ul>06/10/09
  30. 30. Keep your computer Virus free <ul><li>Take care using USB flash cards, CDs, zip and floppy disks </li></ul><ul><ul><li>The more computers flash cards, CDs, zip cards and floppies have been used on, the better the chance of a virus infecting them – clean them before use </li></ul></ul>06/10/09
  31. 31. END 06/10/09