What is a computer virus?
Often, a user isn't aware that his or her computer is infected with a
virus until the virus executes its unique event, such as displaying an unusual message or
damaging a file. It is hard for people to detect viruses because they usually don't
display symptoms prior to the event taking place.
However, some viruses will provide early clues that they exist, such as:
Changes in file or
date stamp.
Longer times to
load programs.
Slower system
operation.
A program fails to
start.
An unusual amount
of disk activity (the floppy or disk drive runs for no apparent reason).