A computer virus is a programme (small or big) which sits on a local host, and is incapable of running independently of that host . This host can be an Operating System or an Application--which is already installed on the PC. For example, a virus may be written in VBScript and sit on CScript or WScript in Windows XP. Invariably, the virus is scripted by a person who has insider knowledge of the structure of the targeted OS/Application. Hence, the easiest and most effective method to ...