Oracle Exploit stop TNS Listener via lsnrctl: If a TNS listener is not password protected everybody can stop the TNS listener (Denial of Service) by sending a STOP command to the TNS listener. This can be done with the lsnrctl command, the tnscmd perl script or via tnsnames.ora.
Even if your TNS listener is protected by a firewall and only accessible via HTTP (e.g. from an application server) it is possible to shutdown the listener,e .g. via iSQLPlus or Oracle Forms, Oracle Reports ...
Solution
Protect your TNS Listener with a password and ADMIN_RESTRICTIONS in the listener.ora.
