Computer Viruses

A computer virus is a program which, after being loaded into a computer's memory, copies itself with the purpose of spreading to other computers.
Most people, from the corporate level power programmer down to the computer hobbyist, have had either personal experience with a virus or know someone who has. And the rate of infection is rising monthly. This has caused a wide spread interest in viruses and what can be done to protect the data now entrusted to the computer systems throughout the world.
A virus can gain access to a computer system via any one of four vectors:
1. Disk usage: in this case, infected files contained on a diskette (including, on occasion, diskettes supplied by software manufacturers) are loaded, and used in a previously uninfected system thus allowing the virus to spread.
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