1. Chapter 5 Protecting Your PC from Viruses Prepared by: Khurram N. Shamsi

2. Computer Virus A Computer virus is a program written for destructive purposes by "mean" people. The virus program is placed into a commonly used program so that the program will run the attached virus program as it boots. The virus "infects" the executable file or program. Viruses work the same ways in Windows or Macintosh machines by infecting zip or exe files. A virus is inactive until you execute an infected program or application. Once a virus is active, it loads into your computer's memory and may save itself to your hard drive or copies itself to applications or system files on disks you use.

3. Some Alarming Facts!!! A computer virus can do extensive damage.  It can crash your hard disk.  It can destroy all or some of your data.  Many viruses do weird little things that adversely affect your computer.  The most usual symptom of a computer virus is erratic behavior.  The destruction can happen at any rate of speed and can affect almost any part of the computer.  Viruses can spread quickly through today's intricate cyber world.  If your computer starts to act a little weird, the first thing to do is to check for a virus.

4. What Virus can do! Some viruses are programmed specifically to damage the data on your computer. They can corrupt programs, delete files, or even erase your entire hard drive. Many viruses do nothing more than display a message or make sounds / verbal comments at a certain time. Many viruses make a programming event after replicating themselves to be picked up by other users one way or another. Some viruses make your computer's system behave erratically or crash frequently. Many people who have problems or frequent crashes using their computers do not realize that they have a virus and live with the inconveniences.

5. What Viruses Don't Do! Computer viruses can not infect write protected disks or infect written documents. Viruses do not infect compressed files, unless the file was infected prior to the compression. Viruses do not infect computer hardware, such as monitors or computer chips; they only infect software. Macintosh viruses do not infect Windows computer software and vice versa. Viruses do not necessarily let you know they are present in your machine, even after being destructive. If your computer is not operating properly, it is a good practice to check for viruses with a current "virus checking" program.

6. How does a computer get a Virus? A computer virus is passed from computer to computer. A virus can be attached to any file that you copy to your computer. If you download files from the Internet or copy programs or files from friends on flash memory, you are very susceptible to viruses. Many viruses are spread through e-mail. A virus normally becomes active when you execute a program that contains the virus.

7. How do Viruses Spread? Viruses begin to work and spread when you start up the program or application of which the virus is present.  For example, a word processing program that contains a virus will place the virus in memory every time the word processing program is run. Once in memory, one of a number of things can happen.  The virus may be programmed to attach to other applications, disks or folders.  It may infect a network if given the opportunity. Viruses behave in different ways.  Some viruses stay active only when the application it is part of is running. Turn the computer off and the virus is inactive.  Other viruses will operate every time you turn on your computer after infecting a system file or network.

8. How to activate a Virus? The trigger that activates the virus can be almost anything.  For instance, the virus can be activated the minute it is installed.  On the other hand, it may initiate its dirty work the next time you start your computer.  In many cases, a virus resides inside your computer in an inactive state, waiting for a certain event to happen.  Like having a physical virus in your body, you can have a virus in your computer system and not even know it. A virus can wait patiently in your system and attack only on a certain date.  Of course, in the time between the moment you contracted the virus and the time it made itself known to you, you may have innocently spread the virus to others.

9. How to stop virus entering your computer? Be smart enough to stop viruses before they enter your computer. Purchase a good virus protection program. An antivirus program can be set to work in the background. It will check all files before they enter your computer and will alert you if a virus is detected before it contaminates your system. If a virus is detected, your antivirus program will quarantine or eliminate it so that it cannot harm your computer. Be very careful to purchase a virus protection program that matches your operating system. If you use Windows Operating System, select a program that was written specifically for your operating system.

10. Steps to protect your computer from viruses To protect your computer from viruses, follow the given steps:  Load the software only from original disks or CD's. Pirated or copied software is always a risk for a virus.  Execute only programs of which you are familiar as to their origin. Programs sent by email should always be suspicious.  Computer uploads and "system configuration" changes should always be performed by the person who is responsible for the computer. Password protection should be employed.  Check all shareware and free programs downloaded from on-line services with a virus checking program.  Purchase a virus program that runs as you boot or work your computer. Up-date it frequently.

11. Suggested Websites http://en.wikipedia.org/wiki/Computer_virus http://www.howstuffworks.com/virus.htm http://support.microsoft.com/kb/129972 http://www.authentium.com http://www.datafellows.com http://www.mcafee.com http://www.symantec.com http://www.antivirus.com