Nowadays, computer viruses are gaining much greater media coverage, as the number of computer viruses is greatly increasing and causing a much greater threat than ever before. The viruses are tiny and do not announce themselves. Therefore, there is no computer software that can detect all the computer viruses in the world. It is for this reason that this book has been created. It aims to clarify how serious the effect of computer viruses really are to businesses and the ways in which viruses can affect different sorts of businesses, offering some suggestion for dealing with the problem. This includes three case studies, explaining how computer viruses have affected three businesses (BT, British Gas and EPSRC), from which general conclusions are produced, highlighting some of the lessons that may be learnt from the case studies. It is hoped that the book will give an insight into such issues, exposing the threats caused by computer viruses and some of the ways to minimize the risks caused by them.