CISSP Practice

Removing malware from within a file.

Disintegration

A physically destructive method of sanitizing media; the act of separating into component parts.

Disk arrays

A technique used to improve the performance of data storage media regardless of the type of computer used. Disk arrays use parity disk schema to keep track of data stored in a domain of the storage subsystem and to regenerate it in case of a hardware/software failure. Disk arrays use multiple disks and if one disk drive fails, the other one becomes available. They also have seven levels from level zero through six (i.e., redundant array of independent disks –RAID0 to RAID6). They use several disks in a single logical subsystem. Disk arrays are also called disk striping. It is a recovery control.

Disk duplexing

The purpose is the same as disk arrays. The disk controller is duplicated. It has two or more disk controllers and more than one channel. When one disk controller fails, the other one is ready to operate. This is a technical and recovery control and ensures the availability goal.

Disk farm

Data are stored on multiple disks for reliability and performance reasons.

Disk imaging

Generating a bit-for-bit copy of the original media, including free space and slack space.

Disk mirroring

The purpose is the same as disk arrays. A file server contains two physical disks and one channel, and all information is written to both disks simultaneously (disk-to-disk copy). If one disk fails, all of the data are immediately available from the other disk. Disk mirroring is also called shadowed disk, and incurs some performance overhead during write operations and increases the cost of the disk subsystem since two disks are required. Disk mirroring should be used for critical applications that can accept little or no data loss. This is a technical and recovery control and ensures the availability goal. Synonymous with disk shadowing.

Disk replication

Data is written to two different disks to ensure that two valid copies of the data are always available. Disk replication minimizes the time-windows for recovery.

Disk striping

Has more than one disk and more than one partition, and is the same as disk arrays. An advantage of disk arrays includes running multiple drives in parallel, and a disadvantage includes the fact that its organization is more complicated than disk farming and highly sensitive to multiple failures.

Disposal

The act of discarding media with no other sanitization considerations. This is most often done by paper recycling containing nonconfidential information but may also include other media. It is giving up control, in a manner short of destruction.

Disruption

An unplanned event that causes the general system or major application to be inoperable for an unacceptable length of time (e.g., minor or extended power outage, extended unavailable network, or equipment or facility damage or destruction).

Distributed computing

Distributed computing, in contrast to supercomputing, is used with many users with small tasks or jobs, each of which is solved by one or more computers. A distributed system consists of multiple autonomous computers or nodes that communicate through a computer network where each computer has its own local memory and these computers communicate with each other by message passing. There is an overlap between distributed computing, parallel computing, grid computing, and concurrent computing (Wikipedia).

Distributed denial-of-service (DDoS)

A denial-of-service (DoS) technique that uses numerous hosts to perform the attack.

A DDoS is a denial-of-service (DoS) technique that uses numerous hosts to perform the attack. An attacker takes control of many computers, which then become the sources (“zombies”) for the actual attack. If enough hosts are used, the total volume of generated network traffic can exhaust not only the resources of a targeted host but also the available bandwidth for nearly any organization. DDoS attacks have become an increasingly severe threat, and the lack of availability of computing and network services now translates to significant disruption and major financial loss.

Distribution attacks

They focus on the malicious modification of hardware or software at the factory or during distribution. These attacks can introduce malicious code into a product such as a backdoor to gain unauthorized access to information or a system function at a later date.

Document type definition (DTD)

A document defining the format of the contents present between the tags in an XML and SGML document, and the way they should be interpreted by the application reading the XML or SGML document.

Domain

A set of subjects, their information objects, and a common security policy.

Domain name system (DNS)