Sys Password and Alter User Privileges

While I am browsing i found this topic which is really amazing and Useful if you are interested securing your database, I mentioned before in my topics to secure database you need to start with simple steps first the below is one of them :

SQL> CREATE or REPLACE TRIGGER prohibit_alter_SYSTEM_SYS_pass
AFTER ALTER on SCOTT.schema
BEGIN
IF ora_sysevent=’ALTER’ and ora_dict_obj_type = ‘USER’ and
(ora_dict_obj_name = ‘SYSTEM’ or ora_dict_obj_name = ‘SYS’)
THEN
RAISE_APPLICATION_ERROR(-20003,
‘You are not allowed to alter SYSTEM/SYS user.’);
END IF;
END;
/

Trigger created.

SQL> conn scott/tiger
Connected.

SQL>alter user system identified by new_password;
alter user system identified by new_password
*
ERROR at line 1:
ORA-00604: error occurred at recursive SQL level 1
ORA-20003: You are not allowed to alter SYSTEM/SYS user.
ORA-06512: at line 5

SQL> alter user sys identified by new_password;
alter user sys identified by new_password
*
ERROR at line 1:
ORA-00604: error occurred at recursive SQL level 1
ORA-20003: You are not allowed to alter SYSTEM/SYS user.
ORA-06512: at line 5