data security and raid

II.I Selected Database Issues: 1 - Security Slide 1/24

Security and Other Technology

DCM Shriram Consolidated Kota

3C13/D6


1. Content

1.1 Objectives

1.2 Scope of database security: why take threats seriously? – 1.2.1 Situations related to database security – 1.2.2 Threats

1.3 Countermeasures: computer-based controls (BRAVE)

– 1.3.1 Backup and recovery

– 1.3.2 RAID technology

– 1.3.3 Authorization

– 1.3.4 Views

– (1.3.5 Encryption – will be covered in next lecture)

1.4 Summary

Content


1.1 Objectives

Objectives

In this Lecture you will learn:

1. The scope of database security

2. Why database security is a serious concern for any organization

3. The types of threat that can affect a database system

4. Which computer-based controls to use for protection


1.2 Scope of database security

Scope of database security: why take threats seriously?

•“Database security”:

• The mechanisms that protect the database against intentional or accidental threats.

• Includes:

• hardware • software• people• data



Situations related to database security

• theft or fraud

• loss of:

– confidentiality: secrecy related to organizations critical data. Breach may lead to loss of competitiveness

– privacy: secrecy related to personal data. Breach may lead to legal action against organization

– integrity: invalid or corrupted data. Breach affects operation of organization

– availability: affects so called 24 x 7 availability, affects financial performance, occasionally causes data corruption



Threats• Threat:

– any situation or event (intentional or accidental) that may adversely affect a system and thus the organization.

• Tangible threat: – loss of hardware, software or data.

• Intangible threat: – loss of credibility or client confidence.



Threats and DamageExtent of damage depends on the existence of • countermeasures, and • contingency plans.

Example: A hard disk crash; all processing must stop until the problem is solved. Recovery time depends on factors such as:• when the last back-ups were taken, and • how easy it is to restore the system.

Organization needs to:• identify types of threats and their significance.• develop appropriate, cost-effective plans and countermeasures.



ThreatsThreats


1.3 Countermeasures: computer-based controls

Countermeasures: computer-based controls

“BRAVE” countermeasures



Countermeasures: Countermeasures: computer-based controlscomputer-based controls

“BRAVE”• B ackup and recovery• R AID technology• A uthorization• V iews• E ncryption NB: despite the wide range of

controls, generally a DBMS is only as secure as its operating system!

Types of countermeasures range from:

–Physical controls to–Administrative procedures



Backup and recovery• Backup: the process of periodically (at frequent and regular

intervals) taking a copy of the database and log files (and possibly programs) on to offline storage media kept in a secure location, suitable for rapid recovery from a fault.

• Journaling: the process of keeping and maintaining online a log file (journal) containing all the changes made to the database to enable recovery to be undertaken effectively in the event of failure.

• Archiving: the process of periodically taking a copy of the database and possibly programs on to offline secondary storage media, suitable for infrequent reference.

• DBMSs provide backup facilities to assist with recovery of the database in the event of failure.



Backup and recovery

• In the event of a failure, the database can be recovered to its last known consistent state using either:

1. The log file created by the journaling facility, or2. The database backup file, or3. Both.

• Without a log file the database would have to be recovered solely from the database backup. This means that any changes made after the last backup to the database will be lost.

• Details of how to restore the database from the log files are given in II.II Transaction Management (lectures 3 & 4).



Integrity• Integrity constraints contribute to maintaining a

secure database by preventing the data from becoming invalid and giving misleading or incorrect results.

• Integrity constraints were discussed in the prerequisite course.



RAID Technology• DBMS hardware needs to be fault tolerant:

– Disk drives, disk controllers, CPU, power supplies and cooling fans.

– Disk drives are the most vulnerable.

• RAID (Redundant Array of Independent Disks)– several independent unreliable disks “look like” one big reliable

disk– organized to increase performance and improve reliability.

• Performance is increased through data striping: – Data is segmented into equal-size partitions (the striping unit). – These are spread across multiple disks– Striping improves overall I/O performance via parallelism.



RAID Technology• Reliability is increased through storing redundant information

across disks using a parity or error-correcting scheme, such as Reed-Solomon codes (Pless, 1989).

1. Parity schemes: – each byte may have a parity bit associated with it that records

whether the number of bits set to 1 is even or odd. – If the number of bits get corrupted, the new parity bit will not

match the stored parity. Similarly, if the stored parity bit gets corrupted.

2. Error-correcting schemes– store two or more additional bits, and can reconstruct the original

data if a single bit gets corrupted. These schemes can be used through striping bytes across disks.


RAID Technology

RAID stands for Redundant Array of Inexpensive (or sometimes "Independent") Disks.

RAID is a method of combining several hard disk drives into one logical unit (two or more disks grouped together to appear as a single device to the host system). RAID technology was developed to address the fault-tolerance and performance limitations of conventional disk storage. It can offer fault tolerance and higher throughput levels than a single hard drive or group of independent hard drives. While arrays were once considered complex and relatively specialized storage solutions, today they are easy to use and essential for a broad spectrum of client/server applications.


The driving factors behind RAID

Number of factors are responsible for the growing adoption of arrays for critical network storage.More and more organizations have created enterprise-wide networks to improve productivity and streamline information flow. While the distributed data stored on network servers provides substantial cost benefits, these savings can be quickly offset if information is frequently lost or becomes inaccessible. As today's applications create larger files, network storage needs have increased proportionately. In addition, accelerating CPU speeds have outstripped data transfer rates to storage media, creating bottlenecks in today's systems.RAID storage solutions overcome these challenges by providing a combination of outstanding data availability, extraordinary and highly scalable performance, high capacity, and recovery with no loss of data or interruption of user access.By integrating multiple drives into a single array -- which is viewed by the network operating system as a single disk drive -- organizations can create cost-effective, minicomputersized solutions of up to a terabyte or more of storage.


RAID Levels

There are several different RAID "levels" or redundancy schemes, each with inherent cost, performance, and availability (fault-tolerance) characteristics designed to meet different storage needs. No individual RAID level is inherently superior to any other. Each of the five array architectures is well-suited for certain types of applications and computing environments. For client/server applications, storage systems based on RAID levels 1, 0/1, and 5 have been the most widely used. This is because popular NOSs such as Windows NT® Server and NetWare manage data in ways similar to how these RAID architectures perform.


RAID 0 • Data striping without redundancy (no protection).

• Minimum number of drives: 2

• Strengths: Highest performance.

• Weaknesses: No data protection; One drive fails, all data is lost.

DRIVE1 DRIVE2

Data A Data A

Data B Data B

Data C Data C


RAID 1 • Disk mirroring.

• Minimum number of drives: 2Strengths: Very high performance; Very high data protection; Very minimal penalty on write performance.

• Weaknesses: High redundancy cost overhead; Because all data is duplicated, twice the storage capacity is required.

Mirroring

Standard Host Adapter DRIVE 1 DRIVE 2

Data A Data A

Data B Data B

Data C Data C

Original Data Mirrored Data


Duplexing

Standard Host Adapter1 Standard Host Adapter 2 DRIVE 1

DRIVE 2

Data A Data A

Data B Data B

Data C Data C

Original Data Mirrored Data


RAID 2

• No practical use. • Minimum number of drives: Not used in LAN

• Strengths: Previously used for RAM error environments correction (known as Hamming Code ) and in disk drives before he use of embedded error correction.

• Weaknesses: No practical use; Same performance can be achieved by RAID 3 at lower cost.


RAID 3

• Byte-level data striping with dedicated parity drive. • Minimum number of drives: 3

• Strengths: Excellent performance for large, sequential data requests.

• Weaknesses: Not well-suited for transaction-oriented network applications; Single parity drive does not support multiple, simultaneous read and write requests.


RAID 4

• Block-level data striping with dedicated parity drive. • Minimum number of drives: 3 (Not widely used)

• Strengths: Data striping supports multiple simultaneous read requests.

• Weaknesses: Write requests suffer from same single parity-drive bottleneck as RAID 3; RAID 5 offers equal data protection and better performance at same cost.


RAID 5

• Block-level data striping with distributed parity. • Minimum number of drives: 3

• Strengths: Best cost/performance for transaction-oriented networks; Very high performance, very high data protection; Supports multiple simultaneous reads and writes; Can also be optimized for large, sequential requests.

• Weaknesses: Write performance is slower than RAID 0 or RAID 1.


DRIVE 1

DRIVE 2

DRIVE 3

Parity A Data A Data A

Data B Parity B Data B

Data C Data C Parity C


RAID 0/1 - RAID 10 • Combination of RAID 0 (data striping) and RAID 1

(mirroring).Note that RAID 10 is another name for RAID (0+1) or RAID 0/1.

• Minimum number of drives: 4

• Strengths: Highest performance, highest data protection (can tolerate multiple drive failures).

• Weaknesses: High redundancy cost overhead; Because all data is duplicated, twice the storage capacity is required; Requires minimum of four drives.


DRIVE 1 DRIVE 2 DRIVE 3 DRIVE 4

Data A Data A mA mA

Data B Data B mB mB

Data C Data C mC mC

Original Data Original Data Mirrored Data Mirrored Data


Types Of RAID • There are three primary array implementations: software-based

arrays, bus-based array adapters/controllers, and subsystem-based external array controllers. As with the various RAID levels, no one implementation is clearly better than another -- although software-based arrays are rapidly losing favor as high-performance, low-cost array adapters become increasingly available. Each array solution meets different server and network requirements, depending on the number of users, applications, and storage requirements.

• It is important to note that all RAID code is based on software. The difference among the solutions is where that software code is executed -- on the host CPU (software-based arrays) or offloaded to an on-board processor (bus-based and external array controllers).


Parity

• The concept behind RAID is relatively simple. The fundamental premise is to be able to recover data on-line in the event of a disk failure by using a form of redundancy called parity. In its simplest form, parity is an addition of all the drives used in an array. Recovery from a drive failure is achieved by reading the remaining good data and checking it against parity data stored by the array. Parity is used by RAID levels 2, 3, 4, and 5. RAID 1 does not use parity because all data is completely duplicated (mirrored). RAID 0, used only to increase performance, offers no data redundancy at all.


A + B + C + D = PARITY

1 + 2 + 3 + 4 = 10

1 + 2 + X + 4 = 10

7 + X = 10

-7 + = -7

--------- ----------

X 3

MISSING RECOVERED

DATA DATA



RAID Technology• RAID 0 –Non redundant. Maintains no redundant data. Has the best write performance since

updates do not have to be replicated. Data striping performed at level of blocks.

• RAID 1 -Mirrored. Maintains two identical copies of the data across different disks (mirrors). Writes not performed simultaneously to maintain consistency in the event of disk failure. Most expensive and slowest storage solution, but very safe.

• RAID 0+1 –Non redundant and Mirrored. combines striping and mirroring.

• RAID 2 -Memory-Style Error-Correcting Codes. The striping unit is a single bit, redundancy scheme used are hamming codes.

• RAID 3 -Bit-Interleaved Parity. Redundancy provided by storing parity information on a single disk. This can be used to recover the data on the other disks should they fail. Parity disk can become a bottleneck though the overall level uses less storage space than RAID 1.

• RAID 4 -Block-Interleaved Parity. Striping unit is a disk block. A parity block is maintained on a separate disk for corresponding blocks from a number of other disks. If one of the disks fails, the parity block is used with the corresponding blocks from other disks to restore the blocks on the failed disk.

• RAID 5 -Block-Interleaved Distributed Parity. Parity data for redundancy is used similarly to RAID 3. The parity data is striped across all disks. Alleviating the bottleneck.

• RAID 6 -P+Q Redundancy. Similar to RAID 5. Additional redundant data is maintained to protect against multiple disk failures. Error-correcting codes are used instead of parity.



AuthorizationAuthorization: the granting of a right or privilege that enables a subject to have legitimate access to a system or a systems object.

Authorization controls (access controls) are built into the software. They govern:

• what systems or objects a specified user can access (e.g. database tables, views, procedures, triggers) and

• what the user may do with them.

Authorization involves authentication of the subjects (potential user or program) requesting access to objects.

Authentication: a mechanism that determines whether a user is who he or she claims to be. A system administrator is usually responsible for allowing users access by creating user accounts. Each user is given a unique identifier The identifier has a password associated with it, chosen by the user and known to the operating system.



AuthorizationProcedure allows access to the computer system but not necessarily to the DBMS or other applications. A separate but similar procedure may be associated with gaining access to these further applications.

The database administrator (DBA) is responsible for authorizing users.

The DBA sets up individual user accounts and passwords using the DBMS itself.

Some DBMSs maintain a list of user identifiers and password distinct from those in the operating systems list.

Others have entries which are validated against the operating systems list based on the current user's identifier. This prevents a user logging on to the DBMS with a different name to that used when logging on to the operating system.



Certain Privileges may be associated with Permission to use a DBMS. For example, the right to access or create certain database objects or relations or to run certain DBMS utilities.

Privileges are granted specific to the requirements of the users job. Excessive granting of privileges can compromise security.

Closed systems: though authorized to use the DBMS, authorization is needed to access specific objects, granted by either the DBA or the owners of the specific objects.

Open systems: users are allowed complete access to all objects within the database. Privileges will have to be explicitly removed to control access.

AuthorizationPrivileges



AuthorizationOwnership & Privileges

• The DBMS owns some objects, usually in the form of a specific superuser such as the DBA.

•Ownership gives the owner all appropriate privileges on the object owned.

•The creator of an object owns the object, and can assign the appropriate privileges.

For example: though the owner owns a view they may be only authorized to query it. (owners set the privileges allowed, and are also subjected to them). Privileges can be passed on to other authorized users.

•In SQL, when a user passes on a privilege, they can indicate whether the recipient can pass it on.




•Different types of identifier may have different associated priorities. For example a DBMS may permit both individual and group user identifiers, and the individual user may have higher priority than the group.

Privileges (Select, Update, Insert, Delete or All) usually have a binary value associated with them (differs from one system to another)

e.g. Select = 0100, Update = 0010, All = 1111. Summing them, for a particular object, indicates the privileges for that user type.

•The different privileges for the different types of user specific to each database object are stored in an access control matrix.



User Identifier Type Group Member Identifier

SG37 User Sales SG37SG14 User Sales SG14SG5 UserSales Group

User Identifier PropertyNo type price ownerNo staffNo branchNo Query Row Limit

Sales 0001 0001 0001 0000 0000 0000 15SG37 0101 0101 0111 0101 0111 0000 100SG5 1111 1111 1111 1111 1111 1111 none

Example:

User group identifiers

Access Control Matrix




Views

• View: a view is the dynamic result of the interaction of one or more relational operations with the base relations, which produce another relation. It is a virtual relation in that it does not exist in the database but is produced upon request by a given user at a particular time.

• The view is a powerful and flexible security mechanism as it hides parts of the databases from certain users.


1.4 Summary

Summary• The Scope of database security:

Why take threats seriously? Situations related to database security The different types of threat

• 1.3 Countermeasures: computer-based controls Backup and recovery RAID technology Authorization Views Encryption – will be covered in the next lecture


Thank You

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