Since the dawn of the computer age the potential for computer viruses to harm your system has been a reality. Though virus attacks seem like a relatively new concept, the vulnerability to those attacks have been around as long as computers could connect to a network, whether a simple computer to computer connection or the wide web connection that is the Internet. In any case the advent of virus attacks seems to have surged because of more media coverage and more users logging on to the Internet. Historically, viruses were directed at a variety of operating systems. Currently though, viruses prey mainly on Microsoft Windows systems. Another difference between viruses of the past and those of the present is the severity of the effect. Pre-1990's viruses affected computers by causing erratic behavior. Today, not only do viruses cause computers to operate differently, they also steal valuable user information like credit card numbers and social security numbers. You can probably understand now why the virus creation industry is bigger now than it ever was before. The new generation of viruses are more dangerous and thus more lucrative to its creators.