We need to establish a few rules between the installation of an operating system and guaranteed that it is stable, between installing an application and using this application. For protection, these rules, must be used by any user. In case that we have network configuration and a link with Internet, there are many problems for information security.
Why are the systems vulnerable? This is the question we don’t have always a good answer at. The security is very difficult and very expensive. That is why not every company has a special budget (security of the information systems is not on the first plan). The security can not be sure 100% and can be inefficient any time.