Symantec Security 5600 Series, Security 5400 Series,Clientless VPN 4400 Series, Administration Manual

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825 Glossary
data transfer The movement of information from one location to another. The speed of transfer is called the data
rate or data transfer rate.
decrypt To convert either encoded or enciphered text into plain text.
denial of service (DoS) attack A type of attack in which a user or program takes up all of the system resources by launching a
multitude of requests, leaving no resources and thereby denying service to other users. Typically,
denial of service attacks are aimed at bandwidth control.
deploy To perform a remote installation.
deployment A process of distributing hardware or software across computers, systems, geographies, or
enterprises.
DES (Data Encryption Standard) A widely-used method of data encryption using a private (secret) key that was judged so difficult to
break by the U.S. government that it was restricted for exportation to other countries. There are
72,000,000,000,000,000 (72 quadrillion) or more possible encryption keys that can be used. For each
given message, the key is chosen at random from among this enormous number of keys. Like other
private key cryptographic methods, both the sender and the receiver must know and use the same
private key.
desktop computer 1. A computer that is used primarily to perform work for individuals rather than to act as a server.
2. A personal computer or workstation that is designed to reside on or under a desktop.
destination port The port to which a TCP or UDP application request is destined. DHCP (Dynamic Host Configuration
Protocol) A method of automatically assigning IP addresses and other network settings to receiving
hosts that contain a DHCP client. This eliminates the need to manually assign IP addresses and other
settings to hosts on a network. Most modern operating systems have a DHCP client.
DH (Diffie-Hellman) A cryptographic technique that enables sending and receiving parties to exchange public keys in a
manner that results in a shared, secret key at both ends. Different strengths are available and are
referred to as Group 1, Group 2, and Group 5 (and higher). DH is used as part of VPN negotiations to
create new keys. See also Perfect Forward Secrecy.
DHCP client The software that enables a computer to receive a dynamically assigned network address from a
DHCP server.
DHCP Relay A proxy that provides DHCP addresses through a security gateway.
dialog box A secondary window containing command buttons and options available to users for carrying out a
particular command or task.
digital certificate A digital certificate is an electronic credit card that establishes a user’s credentials when doing
business or other transactions on the Web. It is issued by a Certificate Authority (CA). It contains the
user’s name, a serial number, expiration dates, a copy of the certificate holder’s public key (used for
encrypting and decrypting messages and digital signatures), and the digital signature of the
certificate-issuing authority so that a recipient can verify that the certificate is real.
digital signature An electronic rather than a written signature that can be used by someone to authenticate the
identity of the sender of a message or of the signer of a document. It can also be used to ensure that
the original content of the message or document that has been conveyed is unchanged. Additional
benefits to the use of a digital signature are that it is easily transportable, cannot be easily
repudiated, cannot be imitated by someone else, and can be automatically time-stamped.
directly connected network A flat network that consists of only one network segment.
DMZ (demilitarized zone) A network added between a protected network and an external network to provide an additional layer
of security. Sometimes called a perimeter network.
DNS (Domain Name Server) proxy An intermediary between a workstation user and the Internet that allows the enterprise to ensure
security and administrative control.
DNS (Domain Name System) A hierarchical system of host naming that groups TCP/IP hosts into categories. For example, in the
Internet naming scheme, names with .com extensions identify hosts in commercial businesses.