Controlling Access to at
A file could be set up to control access to the at command, allowing only specified users to remove, create or show queue information about their at jobs. The file in that controls access to at, is /etc/at.deny. A users listed in this file cannot access "at" commands. Root permissions are needed to edit this file. Thus, the at.allow file can be created in the /etc directory, in that case only users listed in the at.allow file can run at command other than root.
The similar files are available in the SCO and Solaris environments in /etc/cron.d/ directory.