At a certain time, maybe after a set number of executions or on a specific date, the computer virus executes whatever other instructions its author included in it. A benign virus will do no real damage to your computer. They simply conceal themselves and display a message of some sort at some time. Some simply replicate and take up scarce resources such as disk space or CPU time. A malignant virus tries to inflict damage to your computer, although it may not be intentional.
Some computer viruses cause damage due to poor programming and bugs in the viral code.
Malignant viruses may alter one or more of your files or programs so that they do not work properly. The virus may also cause programs to terminate abnormally, cause incorrect information to be written to your documents, alter directory information, delete files, or even erase your entire hard disk. Basically, a computer virus is a threat to the security and integrity of your computer system which could cause the loss or alteration of programs and data and can spread from program to program, computer to computer, or system to system without direct human intervention or even intention. All rights reserved.