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How Viruses Contaminate and Spread Viruses lay dormant on a system until either the infected file is run or the boot sector is read (depending on what type of virus it is). Once the virus is loaded into the computers memory, it is then able to replicate or trigger an event (like erasing files). By using a disk in an infected system, and using the disk in another system, the virus is spread. Although data files may be infected with a virus, and be damaged by it, they themselves can not transfer a virus. Boot viruses and program viruses attack a computer in different ways.
Note: Ignore any e-mails you might recieve warning you not to open messages because the contain viruses. Text, like you see on this page cannot contain a virus. Viruses are programs that must be executed, and displaying text like this will never contain a virus. Beware of file attachments however. Files attached to a message, if ran, could give you a virus. Boot Viruses Every disk that is formatted has a boot sector, even if it is not a bootable disk. When the computer boots and reads an infected drive, the virus is loaded into memory. Also, every subsequent boot will load the virus into memory. Once in memory the virus will attempt to replicate itself and spread to as many files as possible. Boot viruses often go unnoticed for long periods of time because they often don't do any noticeable damage to a computers contents. There are however, some viruses that will erase the boot sector, essentially deleting the contents of the entire drive. Program Viruses Program viruses are different from boot viruses in that they usually attempt to destroy and infect data files instead of erasing the hard disk, filling the hard disk with "garbage" files, or using all available memory. The most prevalent form of program virus today is a "macro" virus. A macro virus is a virus that is written using the applications own programming language. You can only get a macro virus by opening an already infected document.
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