I've inherited a system that has both telnet and ftp enabled. As both these send passwords in cleartext I want to disable them. But many users have never changed their ways to use sftp or ssh. And before I make the change I need to contact them.
What is a good way to see either the number of users or ideally the usernames people are using to login on these services? The best idea I've come up with so far is to grep /var/log/secure. But I'm not sure of what/how to grep this and the high activity has made finding examples difficult. The system is running RHEL 5 if that helps.