VIRUSES

1. VIRUSES Computer Technology Part 5 ERMS 5/13

2. Computer Virus • Set of program instructions that attaches itself to a file, reproduces itself, and/or spreads to other files • It can • Corrupt files • Destroy data • Display irritating messages • Corrupt computer systems ERMS 5/13

3. Spreading Viruses • Viruses spread because people distribute infected files by exchanging disks and CDs, sending e-mail attachments, and downloading documents from the Internet. • Viruses attach themselves to files with .exe, .com, or .vbs filename extensions • When you open aninfected file, the virus opens and waits to infect the next program you run or disk you use ERMS 5/13

4. 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 ERMS 5/13

5. 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 ERMS 5/13

6. Classification of Viruses ERMS 5/13

7. File Virus • Virus that attaches to an application program • Example • Chernobyl • Notorious for overwriting a section of the hard disk, making it impossible to access data • Written by Chen Ging Hau of Taiwan in 1998. One of the most damaging viruses. ERMS 5/13

8. 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 • Created in 1987, written by a university student in Wellington, New Zealand. One of the very first viruses. ERMS 5/13

9. Macro Virus • Macro • A miniature program that usually contains legitimate instructions to automate a document or task. Infects data files—chiefly files created in Word, Excel, Power Point, and even Access. • This virus infects a macro • Example • Melissa Virus • Attaches itself to Microsoft Word documents • Codemas Virus • Attaches itself to Microsoft Excel spreadsheets ERMS 5/13

10. Other Viruses ERMS 5/13

11. 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 • Different tasks that can be affected • Stealing passwords • Deleting files ERMS 5/13

12. Trojan Horse Example ERMS 5/13

13. 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 ERMS 5/13

14. Worm Example ERMS 5/13

15. ERMS 5/13

16. Protecting yourself from viruses • Antivirus software • Set of utility programs that looks for and eradicates a wide spectrum of problems, including viruses, Trojan horses, and worms • Example • McAfee Virus Scan • Don’t open e-mails attachments that have strange names or are from people you don’t recognize ERMS 5/13

17. What kind of Virus? • Jeff has a disk he borrowed from a friend. He puts in the school computer lab and retrieves the data he needs. He turns off the computer and leaves, leaving his disk behind and forgetting all about it. The next morning, Molly comes to the lab and starts the same computer. The computer tries to start from the disk in drive A, and is unable to start, giving Molly an error message. Molly notices the strange disk and takes it out, then tries to start the computer again. But the computer will not start up even when Molly removes the disk. ERMS 5/13

18. What kind of Virus? • David is surfing the internet for some free games. He finds a really awesome game, and it’s FREE! He’s super excited! He downloads the game, ignoring the user agreement and just clicking “yes” without reading it. He plays the game for a while, but then he notices his computer is slowing down and isn’t working properly. There is a virus on his computer! I wonder where it came from? ERMS 5/13

19. What kind of Virus? • Delilah is at the University checking her email in the computer lab. She sees she has several emails and is going through them one by one. One of the emails has the subject line: ILOVEYOU. Wahoo! Someone is in love with her! It’s a love note! YES! Delilah opens the email eagerly. But there was nothing interesting in the email. Before she knows it, a copy of this same email has been sent to all the people in her address book. The next day, the computer lab is closed because it and all the other computers on the network have been infected. Dang it! She has a paper due! Why did they close the lab?? ERMS 5/13

20. What kind of Virus? • Brian is a computer programmer at Synco Systems International. It’s an awesome company and he gets paid really well. He loves his job. He’s just finished writing a new software program for the company that will be used Internationally by hundreds of employees. He loves his job SO much. Three weeks later, Brian is shocked to find out he’s been let go due to “company cutbacks.” Brian is SO ticked off. Strangely, within minutes of Brian’s name being removed from the company database, the software program suddenly goes down, causing a huge breach in the company. Weird. ERMS 5/13

21. Resource Parsons, June Jamrich, and Dan Oja. Computer Concepts. Boston: Course Technology - Thompson Learning, 2002. ERMS 5/13