How to Restrict Job automation(Cron + At ) jobs in RHEL ?

#set user/gruop owner ans permission on crontab
chown root:root /etc/crontab
chmod og-rwx /etc/crontab
ls -ld /etc/crontab
sleep 1
#Restrict at/cron to authorized users
/bin/rm /etc/cron.deny
touch /etc/cron.allow
/bin/rm /etc/at.deny
chmod og-rwx /etc/cron.allow
chmod og-rwx /etc/at.allow
chown root:root /etc/cron.allow
chown root:root /etc/at.allow