Deceptive trade practices.
Misleading or misrepresenting products or services to consumers and customers. In the United States, these practices are regulated by the Federal Trade Commission at the national level and typically by the Attorney General’s Office of Consumer Protection at the state level.

Decryption.
The process of converting encrypted content back into its original form, often the process of converting ciphertext to plaintext. Decryption is the opposite of encryption.

Denial of service attack (DoS).
An attempt by a malicious (or unwitting) user, process, or system to prevent legitimate users from accessing a resource (usually a network service) by exploiting a weakness or design limitation in an information system. Examples of DoS attacks include flooding network connections, filling disk storage, disabling ports, or removing power.

Digital certificate.
A digitally signed statement that binds the identifying information of a user, computer, or service to a public/private key pair. A digital certificate is commonly used in the process of authentication and for securing information on networks.

Digital rights management (DRM).
Any technology used to protect the interests of owners of content and services (such as copyright owners). Typically, authorized recipients or users must acquire a license in order to consume the protected material—files, music, movies—according to the rights or business rules set by the content owner.

Digital signature.
Data that binds a sender’s identity to the information being sent. A digital signature may be bundled with any message, file, or other digitally encoded information, or transmitted separately. Digital signatures are used in public key environments and provide nonrepudiation and integrity services.

Disclosure.
A component of the notice principle, wherein a company should make available its data handling practices, including notices on how it collects, uses, and shares personally identifiable information.

Distributed denial of service (DDoS).
A type of denial of service attack in which an attacker uses malicious code installed on various computers to attack a single target. An attacker may use this method to have a greater effect on the target than is possible with a single attacking machine.

DLL. Dynamic link library.
A set of functions or routines that provide a programmer with a method of accessing, from within the program being developed, data files created by other applications programs such as databases. Commonly used by Microsoft Windows applications.

DNS. Domain Name System.
A system for translating computer names into numeric Internet addresses. A static, hierarchical name service for TCP/IP hosts.

DNS name server.
The servers that hold the DNS name database, and supply the IP address that matches a DNS name in response to a request from DNS client.