What is a Computer Virus?
A computer virus is a section of code that attaches itself to an executable file. The additional code can be destructive (in that it can corrupt files or disks), or it can be something banal, such as displaying a silly message. Whatever happens, they are not desirable items to have on your system! The following list shows what a virus can do:
- Damage, corrupt or delete files from your hard disk
- Copy itself to other programs (known as spawning). This makes the virus spread.
- Alter system settings with the result that your PC fails
- Display unwanted messages
- Corrupt memory causing the system to repeatedly crash
I'd like to make a very important note here before we continue . . .
Not all system crashes and problems with your PC are the result of virus programs — don't become paranoid about it!
Most viruses are found in program files. These are usually .EXE files but can also be included in .COM files. In order for any virus to work, though, it must be loaded into memory and it must be executed (either in its own right or have a program read it).
If a virus program sits on your hard disk and is never run or loaded, it cannot harm your system! Therefore, if you have just downloaded a file from the net, which contains a virus, you won't catch the virus just having it sit there. This means that you have a chance at prevention!
How Do I Catch a Virus?
In order to catch a virus, the infected file must be loaded into memory. That is the first thing. Secondly, it must be executed — in other words, the program has to run. All programs are steps or orders that the computer carries out. This is what is known as running a program.
That's the technical bit. Now what about the important bit? Where do they come from? Viruses can come from anywhere, but you are more likely to find a virus if . . .
- You use pirate software (illegal copies of a program)
- Swap files and programs between friends (which could also be classed as pirating software)
- Buy programs that are ridiculously low in price. What this refers to is if you bought, say, Microsoft Office for £5 (or $5), when the program legitimately costs several hundred pounds (or dollars).
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