ABSTRACT
Most Oracle activity occurs over the network. Oracle clients connect to oracle servers over a communication protocol such as Transmission Control Protocol/Internet Protocol (TCP/IP). Oracle clients and servers communicate using an Oracle protocol called the Transparent Network Substrate (TNS). TNS packets travel as TCP/IP payload. Setting up connections to the database is performed by the TNS listener-or listener for short. Th e listener manages network connections and as such, is the entry point to most database connections. It must be secured properly. Without the listener, your database will not be serving applications. Th erefore, one important aspect of securing the listener involves ensuring that no one hijacks your listener, that no one shuts down your listener, and ensuring that no one cripples your listener by making it do a lot of work that you don’t want it to do (e.g., writing trace information).
