D

DAC
Stands for discretionary access control, a mechanism for controlling access by users to computing resources.

DACL
Stands for discretionary access control list, the most common type of access control list (ACL) used to control access to computer and network resources.

daemon
Under Unix, a program that runs continously in the background, or is activated by a particular event.

daisy-chain
To connect devices together in sequence with cables.

daisywheel printer
A printer that uses a rotating plastic wheel as a type element.

Dark Avenger Virus Writer
A Bulgarian virus writer who invented a polymorphic code--a code that mutates while keeping the original algorithm intact.

dark side hacker
Criminal or malicious hacker, cracker, or blackhat.

data
Information

database
A collection of data stored on a computer storage medium, such as a disk, that can be used for more than one purpose.

database management
The task of storing data in a database and retrieving information from that data.

data bits
A parameter of RS-232 communication.

data communication
The transfer of information from one computer to another.

data compression
The storage of data in a way that makes it occupy less space than if it were stored in its original form.

Data Encryption Algorithm
Symmetric block cipher, defined as part of the U.S. government's Data Encryption Standard.
Data Encryption Standard(DES)
A block cypher employing a 56-bit key to encrypt or decrypt information in 64-bit blocks.

Data-driven Attack
A form of cyber attack encoded in innocuous-appearing data that is implemented by an individual or by software.

datagram
A packet of information transmitted by network.

Data Havens
Concentrations of illegal data in computer services residing beyond copyright protection law.

data integrity
Data meeting an expectation of quality.

data mining
The exploration of databases to find patterns in the data.

data mirror
System whereby data or other disk activity is written to two or more disks simultaneously, so if nobody fails, the data is still available.

data owner
The authority, individual, or organization that has original responsibility for the data by statue, executive order, or directive.

data processing
The processing of information by computers.

Data protection API (DPAPI)
An application programming interface that is part of Microsoft CryptoAPI (CAPI) on Microsoft Windows platforms.

data recovery
The art and technique of recovering part or all of the information lost because of accidental deletion or damage to the storage media.

data security
The protection of data from unauthorized (accidental or intentional) modification, destruction, or disclosure.

data structures
Ways of arranging information in the memory of a computer.

data types
Kinds of information that can be represented in a computer program, such as whole numbers, floating-point numbers, characters, strings, etc.

Davis-Besse Nuclear Power Plant Incident of 2003
In 2003, a worm entered the Davis-Base Nuclear Power Plant computer network located in Lake Erie, Ohio, disrupting the system for more than five hours. Click here for story.

daughterboard
A small circuit board that plugs into a bigger one.

day trading

The practiceof buying stocks or other securities and reselling them within a day (or less) to profit from short term fluctuations.

Dazed and confused
An error message displayed by some versions of Linux upon encountering an apparent hardware malfuntion.

dB
Abbreviation for decibel.

DB2
Popular database management software from IBM.

DB9, DB15, DB25
Designations for the kind of connectors commonly used on serial ports, video cards, and parallel ports respectively.

dBm
Power levelin decibels relative to a level of one milliwatt; used to measure signal strength on telephone lines.

DCOM (Distrbuted Component Object Model)
A Microsoft-developed standard for allowing software components to interact with each other over a network.

DCS-1000
Formerly known as Carnivore, a surveillance technology used by the FBI for monitoring e-mail.

DDE (Dynamic Data Exchange)
In Microsoft Windows and OS/2, a mechanism by which some programs can exchange data with each other while they are running.

DDos (Distributed Denial of Service)
A denial of service attack conducted through a large set of attackers at widely distributed locations.

DDR (double data rate)
Term used to describe a type of SDRAM computer memory that gives faster performance by transmitting data on both the rising and the falling edges of each clock pulse.

.de
Suffix indicating that an email or web address is located in Germany.

DEA
Stands for Data Encryption Algorithm, the name used by the American National Standards Institute (ANSI) for Data Encryption Sandard (DES).

DEADBEEF
The hexadecimal word-fill pattern for freshly allocated memory (decimal -21524111) under a number of IBM environments, including the RS/6000.

dead link
An HTML address that is no longer valid.

deadlock
A situation in which each of two processes is waiting for the other to do something; thus neither one can proceed.

de-Bayerization
The act of decoding an image from a Bayer Matrix to a full-color picture.

deblurring
The use of digital image processing to correct a blurred image.

debug
To remove errors from a computer program.

debugger
A software tool for running programs one step at a time and examining the contents of memory.

deca-
Metric prefix meaning x10.

deception
To present false or forged identity or authentication to break security policy.

deci-
Metric prefix meaning /10.

decibel (dB)
A unit of relative loudness or power.

decimal number
A number expressed in ordianry base-10 notation, using the digits 0,1,2,3,4,5,6,7,8,9, whether or not there are any digits to the right of the point.

declare
To state the attributes of a variable.

declassification
Adminstrative decision or procedureto remove or reduce the security classification of the object or information.

decode
To reverse a previously used encoding process.

decoder
A circuit that recognizes a particular pattern of bits.

decryption Transforming from unreadable to clear.

DeCSS
A program making it possible to copy DVDs encrypted by css.

dedicated
Assigned to only one function.

de facto standard
A standard that is not official but is established by widespread usage.

deface
To mar or alter a website in some undesirable way.

default
An assumption that a computer makes unless it is given specific instructions to the contrary.

default account
System login account that hs been predefined in a manufactured system to permit access when the system is first put into service.

default logic
A formal system of reasoning in which some facts or rules have priority over others.

DefCon
An annual gathering of the computer underground, usually held in Las Vegas, NV, in July or August.

Defense Advanced Research Projects Agency (DARPA)
Organization creditied with developing the Internet.

Defense in depth
A layered approach to implementing network security.

Defense Intelligence Agency
A primary manager and producer of intelligence for the U.S. Department of Defense that was established in 1961.

deform
To digitally manipulate an on screen object so that it is twisted or stretched.

degauss
Demagnetize.

degree measure
A way of measuring the size of angles in which a complete rotation has ameasure of 360 degrees.

Del
The delete key on the keyboard.

delegate (C#)
A variable whose value is a method.

delete
To remove an unwanted item.

delimeter
A character that marks the beginning or end of a special part of a computer program.

Delphi
An object oriented version of the programming language Pascal for developing interactive programs under Windows.

demibold
A typeface weight between ordinary type and boldface.

Demilitarized Zone (DMZ)
In computer networks, the DMZ is a network portion of the network separated from other systems by a firewall.

Denial of Service Attack
A malicious attack on a computer whose purpose is to interfere with the computer's normal functioning, rather than to gain services for oneself or steal confidential data. This is achieved by overloading the target system with invalid, unexpected, or malformed data.

Department of Defense Information Technology Security Certification and Accreditation Process (DITSCAP)
A standardized approach for certifying the security of IT (information technology) systems.

Department of Homeland Security
Organization set up to provide a unifying foundation for the national network of organizations and institutions having the mission of securing the homeland.

depth of field
The ability of a picture to show objects at different distances in focus at the same time.

depth of focus
Tolerance of focusing errors.

Digital Encryption Standard
An encryption system using 56-bit keys in a complicated 16 round substitution process.

DES
Stands for Data Encryption Standard, an encryption standard used for many years by the U.S. federal government.

descender
The part of a character that extends below the baseline.

deselect
To tell the computer you do not want to work with a particular object.

desk accessory
A small, useful program that is meant to be always at hand while you are working at the computer. Examples are the clock, calulator, etc.

deskew
To straighten.

desktop
The whole computer screen, representing your workspace.

desktop publishing
The use of personal computers to design and print professional-quality typeset documents.

DESX
An enhanced version of the Data Encryption Standard

/dev
In Unix, the directory that contains links to specific devices such as disks drives and serial and parallel ports.

device
Any component of a computer that is used for input or output, such as a printer, modem, disk drive, or sound card.

device contention
The situation in which several computer programs, running concurrently, are trying to use the same device at the same time.

device driver
A program that extends the operating system in order to support a specific device, such as a disk or tape drive, video card, or printer.

device ID
A unique name given to a hardware device for use by PLUG AND PLAY and the Windows REGISTRY.

device node
A directory entry, similar to the directory entry for a file but identifying a piece of hardware. In UNIX, the device nodes a found in the directory /dev.

/dev/null
In UNIX, a "device" that is actually a place for discarding data.

dewarp
To straighten or undo.

DH
Stands for Diffie-Hellman, an algorithm used in public key cryptography schemes.

DHCP (Dynamic Host Configuration Protocol)
A protocol for assigning an IP address to each computer automatically as it joins a network, for use as long as it remains connected, rather than assigning a permanent IP address in advance.

Dictionary attack
A technique for cracking passwords.

Diffie-Hellman (DH)
An algorithm used in public key cryptography schemes.

Diffing
A technique used by hackers that compares different versions of files to look for differences.

Digest authentication
A Hypertext Transmission Protocol (HTTP) authentication scheme based on challenge-response authentication

DigiCrime
A website that humorously draws attention to information security issues.

Digital certificate
Encrypted information that guarantees that an encryption key belongs to a user.

Digital fingerprinting
Another name for digital watermarking, a Digital Rights Management (DRM) antipiracy and copy-protection technology.

Digital forensics
The science of applying digital technologies to legal questions arising from criminal investigation.

Digital Millennium Copyright Act (DMCA)
Legislation that extends U.S. copyright law to cover digital content.

Digital Rights Management (DRM)
Any technology used to protect the interests of copyright holders of commercial digital information products and services.

Digital signature
Digital information used for purposes of identification of electronic messages or documents.

Digital Signature Algorithm (DSA)
A public key cryptography algorithm used to generate digital signatures.

Digital Signature Standard (DSS)
A U.S. federal government standard defining how digital signatures are generated

Digital watermarking
A Digital Rights Management (DRM) antipiracy and copy-protection technology.

Disaster recovery plan (DRP)
A plan that helps a company recovery data and restore services after a disaster.

Discretionary access control (DAC)
A mechanism for controlling access by users to computing resources.

Discretionary access control list (DACL)
The most common type of access control list (ACL) used to control access to computer and network resources.

Distributed Denial of Service (DDoS)
A type of denial of service (DoS) attack that leverages the power of multiple intermediary hosts.

DITSCAP
Stands for Department of Defense Information Technology Security Certificate and Accreditation Process, a standardized approach for certifying the security of IT systems.