A computer virus is a program designed to replicate and spread on its own secretly. Usually, you are hardly aware of its existence. Computer viruses spread by attaching themselves to the boot sectors of diskettes and hard disks, to application programs (such as your word processing and spreadsheet programs) or to WORD and EXCEL documents. Information about known virus (e.g. nimda and code red) could be found in http://vil.mcafee.com/