Protect Oracle database server and Listener from distributed denial-of-service(DOS) attack

Malicious clients can attempt to flood database servers with connect requests that consume resources. This is a possible scenario for a distributed DoS attack.

To prevent this scenario, use the SQLNET.INBOUND_CONNECT_TIMEOUT in the sqlnet.ora file and INBOUND_CONNECT_TIMEOUT_listener_name parameters in conjunction.

SQLNET.INBOUND_CONNECT_TIMEOUT should be set to a value in seconds and it determines how long a client has to provide the necessary authentication information to a database because it is possible for connections without authentication to stay open indefinitely.
It is also recommended to set a value for the INBOUND_CONNECT_TIMEOUT_listenername parameter in the listener.ora file to determine how long a client has to complete its connect request to the listener after the network connection has been established.

Then database server terminates the connection if the client fails to establish a connection and complete authentication within the time limit. Therefore, to protect both the database server and the listener, Oracle recommends setting both these parameters in combination.