X
XACML - Extensible Access Control Markup Language (Extensible Markup Language (XML)-based standard used to express security policies and access rights to assets provided through web services and other applications.)
XBL - Spamhaus Exploit Block List (A form of reverse-lookup program or service which provides information about website clients (visitors to a website) in the area of blacklists (real-time blacklist lookups (RBL)). A blacklist is a set of known-bad resources, such as software, executables, disallowed websites, specific types of data, IP addresses, domain names, or applications, which have been listed and explicitly not allowed on a network or host, or are not allowed to be accessed.)
XBRL - Extensible Business Reporting Language (A computer proramming language for business financial data using XML-style tags.)
XDR - External Data Representation (System developed by Sun Microsystems which allows a program running on one computer to execute code on a remote system using a mechanism called a Remote Procedure Call (RPC).)
XGA - Extended Graphics Array (A super video graphics array (VGA) card marketed by IBM for the PS/2. XGA has taken on a more general meaning to refer to any monitor or projector that can display 1024 X 768-pixel images.)
XHTML - Extensible Hypertext Markup Language (A newer formulation of hypertext markup language (HTML) as an extension of Extensible Markup Language (XML) which can involve stricter tag "grammatical" rules, such as opening and closing tags while allowing users more leeway in defining their own set of tags.)
XKMS - Extensible Markup Language (XML) Key-Management Specification (XKMS) (A key management cryptography mechanism which provides protocols for distributing and registering public keys for use with Extensible Markup Language (XML), a markup language for documents containing structured information.)
XMCL - Extensible Media Commerce Language (An XML-based language designed to support the business of delivering digital content, such as music, over the Internet.)
XML - Extensible Markup Language (A markup language which was developed beginning in 1996. A markup language is a way to, not only structure text and data sets, but also to dictate how they will be used. It has served as a foundational and universal standard which provides a structure for other independent markup languages to be built from while still allowing for interoperability. XML can involve stricter tag "grammatical" rules, such as opening and closing tags, while allowing users more leeway in defining their own set of tags.)
XOR gate - Exclusive OR gate (A binary mathematical function commonly used in binary mathematics and encryption methods. A logic gate whose output is 1 when one but not both of its inputs is 1.)
XP - Extreme Programming (A software development model intended to reduce coding errors and increase security at the program level. It is a form of code review during development that takes code reviews "to the extreme" by having them take place continuously, using an approach called "pair programming" in which one programmer dictates to another, who types in the code, allowing both team members to review for errors. XP also relies on writing a minimal amount of code, using a step process which relies on just passing individual pre-written tests, and no more, and then moving to the next code/step test.)
XSRF - cross-site request forgery (Type of attack in which an attacker attempts to steal authentication information from session cookies during the user's current browsing session. The user is usually tricked into visiting a malicious website through redirection or phishing, and the malicious website executes code that attempts to steal authentication information and impersonate the user. This attack requires that the user already be authenticated to the secure site, so that their session credentials are stored in the browser.)
XSS - cross-site scripting (Type of attack in which a victim's computer/browser executes malicious code which has been injected into a vulnerable web page. Usually a victim visits an infected web page and takes some action which allows a malicious script to execute. The most common locations where malicious code will be encountered are online forums, message boards, search boxes, social networking websites, and links embedded in e-mails.)
XST - cross-site tracing
XTACACS - Extended Terminal Access Controller Access Control System (Access control system which allows a remote user to connect and authenticate to a network via an intermediary TACACS server and also separates the authentication, authorization, and accounting (AAA) functions into separate processes, which can be handled by separate servers and technologies.)
XP - version of Microsoft Windows
XP - Extreme Programming (programming methodology/model)
XrML - Extensible Rights Markup Language (language specifying digital content rights/conditions)
XSEDE - Extreme Science and Engineering Discovery Environment (network of computers available for scientific research)
XSRF - cross-site request forgery (type of website attack involving theft of authentication credentials) (security)
XSS - cross-site scripting (type of website malicious code attack) (security)
XTACACS - Extended Terminal Access Controller Access Control System (authentication/access control protocol)
XUL - Extensible User-interface Language (language for defining graphical user interface elements - buttons, dialog boxes)
Y
Z
ZBR - zoned-bit recording (disk formatting technique)
Z-CLV - zoned constant linear velocity technology (optical compact disc recording technique)
ZIF - zero insertion force (chip processor socket installation design requiring no force to install)