There are many users on a full installation of Oracle, most of which you probably won't need. To lock an Oracle user account, you can use the following command:
To unlock the user, simply replace 'lock' with 'unlock'.
For non-critical users, you can always lock and expire the account. We can change the password for, lock, and expire the account CTXSYS all at once:
This will ensure that CTXSYS password has been changed from the self evident default of CTXSYS; on a successful login the password will have to be changed (because it is expired); and because it is locked, he account can't be logged into under any circumstances.
BI - demo user
CTXSYS - Oracle Text/interMedia administrator
DBSNMP - Oracle Intelligent Agent
DSSYS - Dynamic Services and Syndication Server
HR - demo user
MDSYS - Spatial administrator
ORDSYS/ORDPLUGIN - Object Relational Data user
OE - demo user
PERFSTAT - Statspack administrative user
SCOTT - demo user
SH - demo user
TRACESVR - Oracle trace server
WKSYS - Ultrasearch administrator
The best rule of thumb is to install only the features you need when you install Oracle. If you are not going to use Spatial, interMedia, or UltraSearch, don't install them. Then you will not have to worry about those three users.