Unfortunately, the actual damage that viruses cause is usually measured on a personal scale. You may think that one infected machine out of a thousand is a good margin of safety until you find out that it was your term paper or thesis that was compromised or lost. For this reason, it is essential that all users of CIS services be aware of the threat of viruses and what measures will keep them from spreading. Computer viruses may differ in how they are spread and what damage they do. Some take a long time to develop or assert themselves, while others move very rapidly.
Most viruses attach themselves to the formatting areas of floppy disks or in executable programs.
The exact definition of a virus changes about as often as a new strain is reported. Perhaps, a computer virus is best defined as a piece of computer code that hides in places where it should not be, replicates itself gratuitously and then travels to places where it should not go in order to do things that no one wants it to do. Although virus detection software is available to screen for viruses and disinfect disks, the constant introduction of new strains means you should never rule out the possibility of a viral infection, even on well protected systems such as the computers in the CIS computing labs . This usually happens an hour before a paper is due, when the lab is about to close or any time late in the term when there is no time to start a project all over again. Even with scrupulous preventative measures, some nefarious programs may still slip past these defenses and cause great damage.