Securing Listener through a Password

Oracle 9i

When the listener is first created, there is no password by default. The password can be set by two methods: LSNRCTL comand and LISTENER.ORA parameter file.

1. LSNRCTL command

LSNRCTL> change_passord

2. LISTENER.ORA parameter file

passwords_listener =


If you save the change using save_config command, the first method will leave the encrypted password in the parameter file. The second method will always leave the unencrypted password in the parameter file. Once the passwords are changed, you have to supply the password before doing any administrative work. The password must be supplied differently depending on how the password is changed. If the password is changed through LSNRCTL command method, you must supply it like this:

LSNRCTL> set password
Password:
The command completed successfully

If the password is change through LISTENER.ORA parameter file, you must supply it like this:

LSNRCTL> set password

Otherwise, you will get this error:
TNS-01169: The listener has not recognized the password

However, when the password is changed through LSNRCTL command if it is already explicitly specified (unencrypted) in the LISTENER.ORA parameter file, the operation will never be successful. To change the password, you have to remove the line passwords_listener in the parameter file and then change the password.

Use LSNRCTL STATUS command to check if the password is set. If the 'Secrity' setting is shown as ON, then the password is set for the listener.

Reference:
http://www.rampant-books.com/art_nanda_dbazine_securing_listener.htm