DARPA Defense Advanced Research Projects Agency (US)
DCL Digital Command Language, a computer programming language used on
VMS computers
DDN Defense Data Network
DEC Digital Equipment Corporation
DECNET A network protocol used to convey information between (primarily) VAX/VMS machines
DEFCON (a) Defense Readiness Conditions, a system of progressive alert postures in the US; (b) the name of Force's computer program which automatically mapped out computer networks and scanned for accounts
DES Data Encryption Standard, an encryption algorithm developed by
IBM, NSA and NIST
Deszip Fast DES Unix password-cracking system developed by Matthew
Bishop
Dial-up Modem access point into a computer or computer network
DMS-100 Computerised telephone switch (exchange) made by NorTel