You may protect the database from outsiders with a firewall. However, if the access is gained from within the LAN, you will need something that provides security at the source rather than at the perimeter. Oracle Database Firewall provides a first line of defense against attacks like SQL injections and application bypass. Oracle Database Firewall monitors and learns about the normal usage and data access. It can assess the intent of data access and if there is any abnormal activity, it blocks, logs and alerts.
Oracle DB Firewall also helps developers to fine tune the SQL queries as it monitors the execution times, status of the query, errors etc. It can also help while migrating the DB to a new server with the information on the clients accessing the DB. It provides reports for SOX, PCI and other regulations and prevents DBAs from abusing their privileges.
Oracle, Microsoft SQL Server, IBM DB2 for Linux, Unix, and Windows, and Sybase databases are supported by Oracle DB Firewall.