Any Company should be Concern about Powerful user in their company, i am talking here about database users. Specially In Production System.
as we all know Oracle database comes with two powerful account SYSTEM, SYS Very often individual accounts with DBA roles also are created for DBAs to perform their daily duties without using the SYS or SYSTEM accounts.These admin accounts in the Oracle database usually have the ability to manage user security, maintain database storage, and perform backup and recovery tasks.but when the both left without monitored they may perform fraudulent activities without leaving any trace, Stealing Backup, Data or even take look at some personal Data such as Credit card number , Social Number and Mobile number for example.Granting DBA access to business owners is a blatant violation of segregation of duties. However, the list of powerful users should not be limited to these admin accounts. Users with special database privileges such as UPDATE ALL TABLE and SELECT ALL TABLE should also be considered powerful users and should be targets of database monitoring.
usually you need to monitor different activities on your system/applications or database.the best practices of monitoring database for example : logon/logoff activities of SYS/SYSTEM, database schema structure changes and DML (update, insert, delete) on different tables such as tables contain sensentive data ( bank account …. ) .
Oracle Provide with basic and Easy tools to do all the above such:
1- Basic Oracle Audit Trail
By enable AUDIT_TRAIL Parameter ( DB,OS ,NONE) Check Oracle Documentation here, For Example if you set this parameter to OS you should Check AUDIT_FILE_DEST, On another hand if you set this parameter to DB the audit trail will be recorded in a system table named SYS.AUD$ and e SYS user will be audited if the AUDIT_SYS_OPERATIONS parameter is set to TRUE.
Oracle audit utilities allow one to audit by session, user, action and object. also privilege and object can be audited For example, to audit the TEST user’s login activity, one can issue the following statement: AUDIT SESSION BY TEST.In addition to the standard audit features, Oracle’s finegrained audit package DBMS_FGA allows the monitoring of data access based on content. One can specify value-based audit policies using SQL statements while using the finegrained audit package.
2- Create Your Own Trigger
Triggers are database procedures fired off by a specified event. Database triggers can be associated with a table, schema or database. They also can be used as a complementary mechanism to the standard features of Oracle audit facilities
You can enable this feature by command line or by OEM, This utility allow you to receive any error in alert log.
LogMiner Can detect wrongdoings by the database users. Most production databases have turned on the archive log to write archive logs to multiple destinations. The archive logs are used to restore Oracle databases to a point in time. All DDL and DML activities can be reversed using the archive logs. The fraudulent activities of SYS or SYSTEM are recorded there.You can Check V$SQL_TEX.