Bachelor thesis aims to explore and describe the basic principles of SELinux technology. SELinux or Security Enhanced Linux is a technology that enhances the security of Linux systems in such a way that it restricts the set of tasks and files, with which may the given application be working. This is an implementation of so-called managed access control. The work is divided into theoretical and practical part. The theoretical part deals with description of the project status, exploration and summarization of rules or the status of project support of Security Enhanced Linux within Linux distributions. The practical part deals with putting SELinux into operation and evaluation of the security policy tool Multi-Level Security and the subsequent...