Computer virus is a programme created by people which if activated can get into a personal computer without permission of user. These viruses are spread mainly through internet, CD , USB drive or floppy disks. When trojan horses and computer worms usually spread and hack the hosted data contained in websites or even networks. Computers become more vulnerable to viruses due to the internet mediums that connects all computers. The question is who creates them ? Many Anti Spyware companies are behind this activity. They produce these viruses and when people start panicing in fear of this destructive thing, they will introduce their new anti spyware or anti adware product which can overcome this situation. So the answer is simple the creators of these things are the business people itself who wants to make money by making problems and getting attention of people to their products. Be careful when you download softwares or files from internet .Many companies have special viruses that can reformat the disks and install their bugs which will display their advertisements in the computer so that their pop up ads will be displayed. Some people try to hack the datas of other people. We can take thye case of computers in Big Bang Theory experiment which was hacked by some people. Computer manufacturers or competitive manufacturers may also prepare plans to cause destruction of computers so that new computers can be sold out or people will come searching for PC's that cannot be easily attacked by intruders and they will easily sell their products when the fuss is going on.

The ordinary doubt which will come to everyone will be who created the first virus. I have also been thinking of this and did some searching on this topic and found that there are lot of stories and assumptions on this topic. The first virus was born in 1970s. This is what History of Viruses says : The first vastly spread virus was a bootable one called "Brain", the "Vienna" and "Cascade" file viruses appeared later.The first polymorphic virus called "Chameleon" became known in the early '90s, but the problem with polymorphic viruses became really serious only a year after that, in April 1991, with the worldwide epidemic of the polymorphic virus "Tequila". Problems like this are coming up every day. But hopefully there is no problem in this world which does not have a solution.