The UNIX System was designed so that users could easily access their resources and share information with other users. Security was an important, but secondary, concern. Nevertheless, UNIX has always included features to protect it from unauthorized users and to protect users’ resources, without impeding authorized users. These security capabilities have provided a degree of protection. However, intruders have managed to access many computers because of careless system administration or unplugged security holes.
In recent releases, UNIX has included security enhancements that make it more difficult for unauthorized users to gain access. Security holes that have been identified have been corrected.