Section 4 - What is a virus?

A computer virus is a small program written to alter the way a computer operates, without the permission or knowledge of the user. A virus must meet two criteria:

• It must execute itself. It will often place its own code in the path of execution of another program.
• It must replicate itself. For example, it may replace other executable files with a copy of the virus infected file. Viruses can infect desktop computers and network servers alike.

Some viruses are benign; however, most are malignant. 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 resources such as disk space or CPU time. A malignant virus tries to inflict damage to your computer. 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.

Specifically, 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.