How would you like an easy way to determine the last login date for everyone on your system and prepare a list of those accounts that have never logged in at all? If you don’t know the lastlog command, you might be delighted with how easily it can provide this kind of information.
When you think about it, one of the many useful security checks that you can perform on your Linux systems is to determine the last login dates for each of your users. This kind of check can help you to detect potential problems. Accounts that haven’t been used in a very long time, for example, might indicate that those accounts are no longer needed and should be locked; maybe those individuals have changed their job assignments and you weren’t notified. Accounts that are logged into in the middle of the night or when their legitimate users are on a cruise to the Bahamas might indicate another sort of problem altogether.
Read more at ITWorld.