Providing overall system security is not really a separate task for system administrators.
Security is enhanced or compromised by each decision the system administrator makes.
Exercising care and caution contribute to the overall security of the system. Basic tasks, like adding vendor patches and staying aware of bugs in your system can assist you in securing your UNIX environment. Fixing known problems, keeping track of permissions, routinely changing passwords, and documenting your administration and maintenance tasks also contribute to the overall security of your system. Permitting careless use of the root account, not documenting user account creation, permission status, not applying bug fixes and patches, not closing security holes when you find them, creating back-door routes into the host, not logging system activity, not disabling unused accounts, and so on will diminish host security. Much of the security that is provided by the system administrator comes from the regular, routine application of policies and procedures that have been put into place.