A DBMS typically includes a database security and
authorization subsystem that is responsible for ensuring
the security of portions of a database against
unauthorized access. It is now customary to refer to two
types of database security mechanisms:
– Discretionary security mechanisms.
• These are used to grant privileges to users, including the capability to
access specific data files, records, or fields in a specified mode (such
as read, insert, delete, or update).
– Mandatory security mechanisms.
• These are used to enforce multilevel security by classifying the data
and users into various security classes (or levels) and then
implementing the appropriate security policy of the organization.
– For example, a typical security policy is to permit users at a certain classification
(or clearance) level to see only the data items classified at the user’s own (or
lower) classification level. An extension of this is role-based security, which
enforces policies and privileges based on the concept of organizational roles