Establishing Security Controls in a Distributed Database - High-Performance Web Databases: Design, Development, and Deployment - page 750

The objectives and benefits of DDBSs include:
• Increased system availability and better performance.
• Higher system throughput.
• Improved disaster recovery.
• System reliability.
• Reduced communications costs.
• Information-sharing capabilities.
• Distribution of certain applications.
• Flexibility and extensibility.
• Local control.
• Incremental database growth.
These benefits do not come without a price, however, and the distrib-
uted nature of the database is the source of most of the problems of DDBSs.
These problems include higher operating costs, communications delays,
consistency (i.e., update) problems, concurrency control, and data secu-
rity problems. Compared to a centralized database, a distributed database
is much more vulnerable to possible security threats — for example, theft,
invasion of privacy, updating, and unauthorized access — because of the
dispersed structure of its data.
Data can be distributed over multiple computer systems in three ways:
through replication, partitioning, or allocation. Replication implies that the
same copy of the database is stored in each of the sites or nodes in the com-
puter network. Partitioning, however, means that data is stored in the site
where it is most needed. Partitioning is sometimes known as data fragmenta-
tion, whereby logically related sets of data are stored in the same site. Alloca-
tion is a hybrid of partitioning and replication. Each method has its own impli-
cations for data recovery, updating and concurrency control, system
reliability and availability, data security and integrity, and transmission costs.
SECURITY THREATS IN A DISTRIBUTED DATABASE
The basic threats to the security of data in a distributed database envi-
ronment are not very different from those affecting centralized computer
systems. They include crime, employee negligence, accidents, technical
faults, viruses and worms, environmental factors, and natural disasters.
However, certain characteristics of distributed databases (e.g., increases
in the points of entry to the system, in user autonomy, and in the number
of users) create additional security concerns.
The consequences of security violations can be classified into the following:
• Loss or destruction of data.
• Theft of data.
• Corruption or modification of data.