In order to know, which listener commands were executing, one should enable the logging by the following:
LSNRCTL> set log_directory …/log
LSNRCTL> set log_file Listener_<sid name>.log
LSNRCTL> set log_status on LSNRCTL> save_config
Setting Listener Password is strongly recommended in order to prevent the distinct attacks. There are two ways to do the same. Either by setting PASSWORDS_listenername parameter in listener.ora file (Password will be in a Clear Text – Not Recommended)Or By using lsnrctl set password command (Highly Recommended).
Since listener.ora files are usually copied between # of instances, they may contain old and redundant entries. Remove any services not currently being used.
Setting this parameter in Listener.ora file to ON will prevent any runtime modification. One can not execute any SET command either Locally or Remotely.
It is no doubt one of the powerful tools to restrict the Traffic from Listener. It can be achieved by the following:tcp.validnode_checking = yes (to enable Valid Nodes Checking)tcp.invited_nodes = (Nodes where Access Allowed)tcp.excluded_nodes= (Nodes Where Access Restricted)Either Use Invited_Nodes or Excluded_Nodes but Do Never Use the Both.
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