For the first few decades of their existence, computer networks were primarily used by university researchers for sending e-mail and by corporate employees for sharing printers. Under these conditions, security did not get a lot of attention. But now, as millions of ordinary citizens are using networks for banking, shopping, and filing their tax returns, network security is looming on the horizon as a potentially massive problem.
The requirements of information security within an organization have undergone two major changes in the last several decades before the widespread use of data processing equipment, the security of information felt to be valuable to an organization was provided primarily by physical and administrative means. With the introduction of computer the need for automated tools for protecting files and other information stored on the computer became an evident this is especially the case for a shared system, such as time sharing system and the need is even more acute for systems that can be accessed for a public telephone or a data network. The generic name for the collection of tools to protect data and to thwart hackers is "computer security".