This 4-page, 5-source paper provides an overview of computer operating system security. Written at a high school level, the author begins by discussing some of the security problems inherent in workstations and across networks. Then, the author discusses three major operating systems: Windows 95, Linux/UNIX, and Windows NT, briefly touching upon the security features and weaknesses of each. An outline is provided. 4 pgs. Bibliography lists 5 sources.