computer viruses are programs that can replicate,duplicate and copy itself by rapid multiplications without the users knowledge and permissions.In the recent times many adwares,malware and spywares are also classified wrongly into viruses but there is a distinct difference between them.Whats special about computer viruses is that they may multiply themselves as well as inject that factor into other healthy files thereby making them also viruses.The spread of viruses from one system to another is only by means of contact either by means of networks, internet and LANS or by means of removable memory devices like USB disks, floppy disks, Compact disks and so on.With the advent of the Internet and the World wide web, almost all the personal computers are connected to the Internet thereby easing the chance of virus attacks.The viruses can also transfer via e-mails,chat programs,file sharing programs and so on.In the early 1970s ,the Creeper virus was the first one detected in the ARPANET, the primitive form of the Internet what we know today.It displayed the text message ” I’M THE CREEPER : CATCH ME IF YOU CAN.”after infecting the system via the ARPANET.Now a days there are advanced forms that you might have noticed that sends links to other websites to your mailing list every now and then when you are online using that chat client.