Port 1521

Port 1521 is designated as ncube-lm for the nCube License Manager by the IANA , but is also used by Oracle. Oracle uses the port for the Oracle Transparent Network Substrate (TNS) protocol, which is used between a database server and database client applications. SQL*Net (Oracle 7) and Net8 (Oracle 8) are examples of TNS enabled applications.

References:

  1. Connecting with Oracle: Oracle Ports
    By Steve Callan
    April 8, 2004
    Database Journal
  2. Identifying Oracle database installations during a network scan
    By Mark Rowe
    Pentest Limited
  3. "NERP" DoS attack possible in Oracle
    August 27, 1998
    Denial of Service Database
  4. Unix Tip: Finding services on a subnet
    By Sandra Henry-Stocker, ITworld.com
    May 14, 2007
    openitworld.com
  5. Cisco PIX: Advanced Features and Attack Guards
    By Andy Fox, David W. Chapman
    December 28, 2001
    Cisco Press