How to identify unused or expired DBMS accounts?

  To maintain security and avoid unauthorized access to database I need to identify unused or expired DBMS accounts. I need to monitor DBMS accounts with DEFAULT profile and if they are inactive for 30 days I need to print the list of them. Then I will need to lock and to expire them and consider dropping them after receiving authorization from applications' administrators. Can you suggest the best approach? I would like to have a script (or sequence of scripts/steps) that could eventually print for me the list of these suspicious accounts.
Victor