Install OpenSSH as a Telnet Replacement
Telnet is a notoriously insecure protocol. Data, including passwords, are passed in cleartext. Replace telnet with OpenSSH. OpenSSH is an open source version of the SSH protocol. OpenSSH encrypts all traffic, including passwords, to effectively eliminate eavesdropping connection hijacking, and other network level attacks.
Disable cron and at Jobs Except for root
Make sure the entry CRONLOG=YES in /etc/default/cron.
Remove all files except root's from /var/spool/cron/crontabs.
Create at.deny and cron.deny in /etc/cron.d. Make the two files owned by root with permissions rw-r--r--. The contents of the file should include the userids that are not permitted to submit batch or run cron jobs. As a starting point set the files up to look like this:
daemon
bin
smtp
nuucp
listen
nobody
noaccess
Disable NFS File Sharing Services
Remove the file /etc/dfs/dfstab to disable NFS exports.
Make sure the file /etc/rc3.d/S15nfs.server has been removed to prevent the host from acting as an NFS server.
Make sure the file /etc/rc2.d/S73nfs.client has been removed to prevent the host from acting as an NFS client.
Reboot the System
Now it's time to reboot the configuration of the system. Reboot the system and observe the boot up process in particular, what processes startup. After the system is up, log in and do ps -ef. Check for extraneous processes. Also, check /var/adm/messages.
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