D

Data Encryption Standard (DES)

A method of data encryption that relies on symmetric key encryption. This methodology was originally introduced in 1975 and standardized by ANSI in 1981.

Data Range

The list of acceptable values for any variable including control properties. A data range determines the set of data inputs that will work with a particular variable. For example, if a variable accepts only characters, the data range would include the letter A, but not the number 1.

Data Stream

One of several methods to send or access information that resides either in local or remote storage. A data stream consists of a series of bits taken from any location within a data storage unit (such as a file). The information can flow continuously (as in an Internet transfer for music) or in blocks (as occurs when reading data from a file on the local hard drive). The reading and writing sequence need not use blocks of any given size and the transfer often works with individual bits rather than characters or words.

Database Management System (DBMS)

A method for storing and retrieving data based on tables, forms, queries, reports, fields, and other data elements. Each field represents a specific piece of data, such as an employee’s last name. Records are made up of one or more fields. Each record is one complete entry in a table. A table contains one type of data, such as the names and addresses of all the employees in a company. It’s composed of records (rows) and fields (columns), just like the tables you see in books. A database may contain one or more

related tables. It may include a list of employees in one table, for example, and the pay records for each of those employees in a second table. Sometimes also referred to as a Relational Database Management System (RDBMS) that includes products such as SQL Server and Oracle.

DBMS

See Database Management System

DCOM

See Distributed Component Object Model

DDoS

See Distributed Denial of Service

Declarative Security

A type of .NET Framework security that relies on attributes to declare the security requirements of an assembly, class, property, event, or other major application element. The compiler evaluates the attribute at compile time and places a token for the security requirement in the assembly manifest. This feature makes it easy to determine security requirements before the application runs. However, declarative security can open an application to possible review by crackers. In addition, it’s less flexible than using in-code security programming such as imperative security.

DER

See Distinguished Encoding Rules

DES

See Data Encryption Standard

Deserialization

The act of converting a serialized data stream into an object using the class description as a template. The application performing the conversion must have access to the class template and know the method of serialization.

Digital Certificate

A specially encoded key pair used to identify a caller. A Certificate Authority (CA) issues the digital certificate on behalf of the caller after verifying the caller’s identity. The recipient must trust both the caller and the CA before digital certificate can lend credence to the source of the transmitted data. The most common use of digital certificates from a user perspective is as an email attachment that enables the recipient to identify the caller with confidence. However, digital certificates are also used in other forms of data exchange.

Digital Signature Algorithm (DSA)

The mathematical basis for encrypting and decrypting digital signatures used with the Digital Signature Standard (DSS) introduced by the National Institute of Standards and Technology (NIST). DSS also relies on Secure Hashing Algorithm 1 (SHA-1) to provide the hashing functionality.

DISCO

See Discovery of Web Services

Discovery of Web Services (DISCO)

A service associated with the Internet that’s designed to make it easier to locate and use SOAP services. This particular service is SOAP specific and a single vendor, Microsoft, currently supports it. The DISCO service relies on a special protocol named SOAP Contract Language (SCL) to allow the discovery of services by remote computers.

Distinguished Encoding Rules (DER)

A technique for exporting a digital certificate from a memory or other data store to disk. The most common way to use this technique is to encode ASN.1 objects into a sequence of octets. DER provides unique encoding for all ASN.1 values.

Distributed Application

An application that resides on more than one machine; normally a client and server, but not necessarily limited to this configuration. The application could include

multiple levels of clients and servers, commonly referred to as tiers. The application is composed of multiple interchangeable elements. For example, a server component could service more than one application type. The application elements are loosely coupled (both systems only require access to self-describing messages) and the developer can replace each element with updates as needed as long as the new element provides the same interface to the client.

Distributed Component Object Model (DCOM)

A transport protocol that works with the component object model (COM), and is used for distributed application development. This protocol enables data transfers across the Internet or other non-local sources, but is usually limited to a Local Area Network (LAN) or Wide Area Network (WAN) environment. DCOM adds the capability to perform asynchronous, as well as synchronous, data transfers between machines. The use of asynchronous transfers prevents the client application from becoming blocked as it waits for the server to respond.

Distributed Denial of Service (DDoS)

A specialized form of DoS attack where the cracker relies on a multitude of zombie machines to perform a denial of service attack on a target network. The cracker may not even know how many machines are involved in the attack since this technique often relies on virus programs to install the required software on an unsuspecting host.

DLL

See Dynamic Link Library

Document Type Definition (DTD)

A document that defines how an application should interpret markup tags within an HTML, XML, or SGML document. In some cases, such as HTML, the DTD is an actual specification. In other cases, such as XML, the DTD is an external document supplied by the user or the vendor. A DTD can define every characteristic of a document as long as those characteristics are defined using standard tags and attributes.

Domain

An area of control in a network. Members of a domain can share resources controlled by one or more member servers. One or two servers normally control the security of the network; these servers are normally called domain controllers.

DSA

See Digital Signature Algorithm

DTD

See Document Type Definition

Dynamic Link Library (DLL)

A specific form of application code loaded into memory by request. It’s not executable by itself like an EXE is. A DLL does contain one or more discrete routines that an application may use to provide specific features. For example, a DLL could provide a common set of file dialogs used to access information on the hard drive. More than one application can use the functions provided by a DLL, reducing overall memory requirements when more than one application is running. DLLs have a number of purposes. For example, they can contain device-specific code in the form of a device driver. Some types of COM objects also rely on DLLs.