Prevention to keep viruses from entering a computer. Creating user awareness. Controlling which disks are used in a computer. Using one technique is never 100 percent safe. Detection A dependable method of detection is necessary to catch viruses that do pass preventive measures.
Personal observation is important.
The size of a program changes. The disk runs out of free space when it seems to have plenty. Bit errors occur frequently while running Windows. The disk drive is active when it should not be. The hard drive is inaccessible when booting from a floppy drive.