A new Oracle default password checking tool is available
This default password list is probably the biggest Oracle default password list available. How does it work? The set of scripts creates a user, a table to hold details of the default users and also then creates a simple package procedure that loops through all of the users in the database and compares them with the default users in the created table. A useful report is printed showing any default users found with known passwords and details of what the user is used for.
The script download can be found here. The page also describes in detail the problem and also each script in the download. The page also describes how it works and shows a sample session.