Computer Terminology

The following is a list of many cumputer tech terms.

Address	An address in memory is a location to which an application or a piece of hardware refers. For example, a word processor will store your document in a particular memory address while you have it open. Problems occur when two things (hardware or software) try to use the same address.
Anonymous FTP	This is a method of using FTP without a password. Anyone who wishes to make files publicly available can allow users to use FTP by specifying anonymous for the user name, and their email address for the password.
Applet	Quite simply, a small application. For example, each of the windows that appear when you double-click on an icon in Control Panel are considered Applets, because while they are small applications by themselves, they require a larger application (Control Panel) to operate them.
Application	Any program on your hard disk - an application usually has its own Directory and can be started by clicking on its icon in the Start Menu. Most applications have their own Window.
BIOS	Short for Basic Input-Output System; this is a chip (or set of chips) in your computer that controls how your computer communicates with some of the basic hardware componentes in your system, such as the keyboard, floppy drive, and hard disk. In newer computers, the BIOS is also what supports Plug-&-Play. A buggy or incompatible BIOS is a common cause of problems encountered when upgrading to a new version of Windows.
Boot	The process of starting up a computer. See Reboot.
Browser	A winsock client (software) used to navigate the World Wide Web. Netscape, Mozilla, and Internet Explorer are examples of browsers.
Buffer	The use of part of your computer's memory to relieve the burden on a specific component, such as your keyboard or printer. For example, if you press all of the keys on your keyboard at once (on a slow computer), the letters would appear on the screen slower than you've typed them. Since the computer isn't able to process keys that quickly, they keys you've pressed are stored in a buffer and fed to the computer at a slower rate it can handle - this way, your keystrokes aren't lost. Note that your computer will beep if the buffer is full, telling you keys pressed thereafter will be forgotten. Similar to Cache.
Bug	An error in software that causes it to work improperly or not at all. This term comes from an occurance when an actual bug made a nest in an early hard-wired (without software) computer, causing it to malfunction.
Button	A 3-D control on the screen that looks like it's pushed in when you click on it. This is different from an icon, although buttons can contain icons. Buttons usually get a single left-click, while icons get a double-click.
Byte	The smallest unit of storage, either on a disk or in memory. For example, in a document created by a word processor, each character takes up at least one byte. See megabyte, kilobyte, and gigabyte.
Cache	The use of part of your computer's memory to improve the performance of a specific component, such as your hard disk, CD-ROM drive, or even your processor. By storing recently acessed information in a disk cache, for example, your computer can respond faster because it is accessing memory, instead of the slower hard disk. (pronounced "cash") Similar to Buffer.
Character	A letter, number, or symbol - anything that can be typed from the keyboard.
Client	1.) An appliction used over a Winsock connection, such as an email program or a World Wide Web Browser. 2.) A computer (hardware) on a network that isn't a server.
Cluster Size	This is the smallest amount of hard disk space a file can occupy. Floppies have a cluster size of 512 bytes and hard disks can have a cluster size ranging from 1 kilobyte to 16 kilobytes (sometimes even more). The larger the partition, the larger the cluster size. See Slack Space.
CMOS	A small bit of memory used by your computer used to store certain settings while it's turned off, such as the type of hard disk installed. You can typically change the CMOS settings by pressing a certain keystroke (such as Del or ESC) during the system boot.
Command Prompt	One of the simplest ways to control a computer. The user runs applications and performs other activities by typing commands at a prompt. Unix and DOS are examples of command prompts.
Context Menu	The menu that appears when you right-click on an object, such as a folder or a file. It's called a context menu because the items in the menu depend on what's being clicked - the menu is appropriate to the context.
Control	An element of the user interface, such as an icon, a button, or a window.
Cooperative Multitasking	A type of multitasking where the operating system assigns an equal amount of processor cycles to each application, regardless of how much power it actually needs. Preemtive multitasking (used in all modern versions of Microsoft Windows) is more efficient than the cooperative multitasking found in Windows 3.1.
CPU	Central Processing Unit - this is another name for the processor.
database	A collection of information stored in an organized fashion, suitable for updating and viewing the information contained within frequently and easily. A database application is required to access the information in a database.
DDE	Short for Dynamic Data Exchange; the method by which different applications can communicate with eachother. For example, installation programs use DDE to communicate with your Start Menu (or the Program Manager in Windows 3.x) to add new program icons. See OLE.
Default	An original, factory setting. For example, the taskbar is located at the bottom of the Windows screen by default, but you can move it to any side of the screen by dragging it with the mouse.
Defragment	Using the Disk Defragmenter application, you can fix all the files on your hard disk that have become fragmented . When many files become fragmented, your hard disk performance is slower, and the danger of file corruption is greater, so it is a good idea to defragment often. This is also known as Optimizing your hard disk.
Desktop	The blank area on your screen behind all the windows. The dekstop can hold icons, because it is really a directory on the hard disk. Right-click on the desktop to change its many properties.
Directory	A container for files - it can have any name, but always has a yellow folder for its icon. Also called Folder. Every directory has its own icon, into which other icons can be dropped.
Disk	A storage device used to hold files and directories. There are hard disks and floppy disks.
Diskette	Another name for floppy disk.
Document	This is the file you create in an application - an example is a letter that you've written in a Word Processor. Every document has its own icon.
DOS	Disk Operating System - the first Operating System available for the PC platform. See Command Prompt. Easily recognized by the C:\> prompt.
Driver	A piece of software that assists your computer in using a specific device, such as a printer or scanner. Buggy drivers cause the majority of problems with a computer.
Email	A method of sending and receiving personal messages over a networks, such as the Internet.
Explorer	The primary interface for Windows - this includes the folders in My Computer and the items in the Task Bar, as well as the window with the tree view.
Extension	The part of a filename that follows the period "." - this allows Windows to determine what type a file is. For example, a file with the .TXT extension tells Windows that it is a text file. Extensions are hidden by default; here's how to display them.
FAQ	Short for Frequently Asked Questions, a collection of questions and answers commonly used in World Wide Web sites, newsgroups, and other discussion forums.
File	Files contain data, whether it's a document you've written, or an application used to create the document. Every file has its own icon. Files are stored in folders.
Finger	Finger is a very old way of looking up someone's email address on the Internet. Assuming a user's ISP supports it, fingering a user on the internet displays the last time the person logged in, and whether or not he or she has any mail to be read. There also may be special information displayed if the user has set up a Plan file. You need a Finger client (software) to use this feature of the Internet.
Floppy Disk	This is an inexpensive, removable disk that has a much lower capacity and speed than a hard disk. Its capacity can be measured in kilobytes or megabytes.
Folder	Interchangable with Directory, although folder is a newer term.
Fragmented	When a file has become fragmented, it means that it is broken up into pieces on your hard disk. Imagine if you saved a file to your hard disk, and then saved another right after it. When you go to add more to the first file and then save it again, it no longer can fit in the space allotted, and must be split apart. When many files become fragmented, your hard disk performance is slower, and the danger of file corruption is greater. To fix fragmented files, you must defragment your hard disk.
FTP	File Transfer Protocol - a method of transferring files from one computer to another across the Internet. You need FTP client software to use FTP. Windows comes with a simple DOS-based FTP client, FTP.EXE. Anonymous FTP is the most common use of FTP.
GB	An abbreviation for Gigabyte.
Gigabyte	One billion bytes, or more precisely, 1,024 megabytes (totalling 1,073,741,824 bytes). Different definitions of this term cause distrepencies between different manufacturers and applications.
GUI	Short for Graphical User Interface; a type of user interface that uses graphics (such as icons and windows) to control the computer. Windows uses a GUI.
Hard Disk	This is a disk that is permanently connected to your computer, and has a much higher capacity and speed than a floppy disk. Its capacity is measured in megabytes, and can be divided into several partitions.
Hardware	A general term used to describe the equipment that makes up and is connected to your computer. To the beginner, software is what ever you see on the screen, and hardware is everything you can touch.
Icon	The little pictures that you see on the screen, usually representing folders and files - icons can be dragged onto other icons, onto applications, and into folders. Icons usually get a double-click, while buttons get a single left-click.
Interface	The method by which you control anything. The screen is the interface to your computer, just as a dashboard is the interface to your car, just as a doorknob is the interface to a door. See User Interface.
Internet	An term used incorrectly to describe the World Wide Web - the Internet is a WAN, and a superset of the World Wide Web. Originally connecting a few universities and the United States government, it was designed to provide a network that could withstand a war, because of its decentralized structure. See email, telnet, and ftp.
Interrupt	A method by which a piece of hardware communicates with the processor. It's called interrupt, because the device (such as a sound card) interrupts the computer to carry out a function (such as playing a sound). See IRQ.
IRQ	Short for Interrupt Request Line; A number used to describe an interrupt. An IRQ can be any number from 0 to 15, inclusive. IRQ problems occur because two pieces of hardware try to use the same IRQ.
ISP	Short for Internet Service Provider; these are the folks who bill you for access to the Internet. If you have free Internet access through a university, then the university is your ISP. Tip: look for an ISP that doesn't charge by the hour!
KB	An abbreviation for Kilobyte.
Kilobyte	One thousand bytes, or more precisely, 1,024 bytes.
LAN	Local Area Network - a network with all its computers close together (geographically).
Lost Chains	Pieces of files that are no longer being used, but are still taking up disk space. Use Scandisk to clean up your lost chains and delete them. If you convert them to files, they will have the CHK extension - these files will be useless to you unless you know how to retreive your data from them.
Marketing	The only way a company with a customer satisfaction rating as low as Microsoft's could be so successful.
MB	An abbreviation for Megabyte.
Megabyte	One million bytes, or more precisely, 1,024 kilobytes (totalling 1,048,576 bytes).
Memory	Also known as RAM, this is what allows your applications to run. The more memory you have, the more windows you can have open, and the more applications you can run simultaneously. Memory, while not the same as disk space, is also measured in bytes, kilobytes, and megabytes.
Menu	A list of things that an application does. In Windows, nearly every application has a menu along the top of its window, usually containing the items File, Edit, View, and Help - when clicked, additional subordinate menu items are displayed.
MRU	This isn't as much of an actual term, as it is a frequently-seen acronym in the. It stands for Most Recently Used, and is generally used in conjunction with lists of stuff you've recently typed in. For example, there's an MRU list for the things you've most recently typed into the Start Menu's Run command.
Multitasking	An operating system performs multitasking when it runs more than one application simultaneously. See Preemtive Multitasking, Cooperative Multitasking, and Multithreading.
Multithreading	The method by which an operating system is able to run different parts of the same application simultaneously. See Multitasking.
Network	A network is what you get when you connect two or more computers together - the Internet is a type of network. The terms LAN and WAN describe the geographic scope of the network.
Object	A general term used to describe almost everything on the screen. In a stricter sense, objects are used in an object-oriented design.
Object-Oriented	An overused term, originally used to describe an advanced method of computer programming. For example, the interface in Windows is considered to be sortof object-oriented, because files and most of the controls are treated as strict objects, each having its own property sheet.
OLE	Short for Object Linking and Embedding; a method by which applications can share information. Basically, it allows you to Cut something from one application and Paste it into another, and then edit the object in place. This second-rate technology (invented and pushed by Microsoft) has been known to cause Pentium-class systems to behave like 286's, and is responsible for much of the unecessary complexity found in Windows and Windows Applications. See DDE and Marketing.
Operating System	The software used to control a computer and run applciations. Windows, DOS, and Unix are all examples of operating systems.
Partition	A division of a hard disk. For example, a 500 megabyte hard disk can be divided into two 250-megabyte partitions. Smaller partitions can be used to further organize files and reduce the cluster size.
Ping	From Navy terminology, ping is used to find out if a machine on the Internet exists and is responding. To use this feature, open a DOS window while you're connected, and type FINGER WWW.CREATIVELEMENT.COM (or any other server). Ping will send small pieces of information to the machine, and you know if the server is "up" if you get a response.
Preemtive Multitasking	A type of multitasking where the operating system assigns processor cycles to applications depending on how much power they need. Preemtive multitasking is used in Windows, and is better than the less efficient cooperative multitasking found in Windows 3.1. However, only 32-bit applications can take advantage of this feature.
Processor	This is the chip in your computer that does all the calculations - for Windows users, it's based upon Intel's x86 architecture, which includes the 386, 486, and Pentium series. This is also referred to as the CPU.
RAM	Short for Random Access Memory - this is the main type of memory in your computer. See ROM.
Reboot	The process of re-starting your computer. If you turn it off and then on again, or use the reset button on the front of your computer, it's called a cold boot. If you hold Ctrl and Alt while pressing Del, it's called a warm-boot. See Boot.
Registry	A complicated database of settings for use in Windows. You can edit these settings with the Registry Editor, REGEDIT.EXE. The registry is stored in two files in your Windows directory, USER.DAT and SYSTEM.DAT.
ROM	Short for Read-Only Memory - this is a type of storage or memory that can only be read, not written to. A CD-ROM is an example of a ROM storage. See RAM.
Root Directory	The top-level directory in the tree. For drive C:, the root directory is signified by a single back-slash: C:\.
Server	A computer on a network that handles a specific function for the rest of the network. For example, a print server can allow all the computers on a LAN use a printer. A World Wide Web server contains pages (like what you're viewing) that are sent to other computers on the Internet for viewing.
Shortcut	A small file that allows you to put an icon for an application in a directory other than the one containing the application. You can also make shortcuts to folders and files. Useful places for shortcuts are the desktop and the Start Menu. You can tell a shortcut from other icons by the little curved arrow in the lower-left corner. For those users familiar with Unix, this is similar to a symbolic link.
SIMM	Short for Single Inline Memory Module; a SIMM is a small circuit board that holds memory chips. Rather than installing individual chips to increase your system's memory, you install SIMMs, which are much easier to install and remove. Nearly all newer computers (those capable of running Windows) use SIMMs.
16-Bit	In reference to Windows applications, a method by which an application uses your computer's memory and communicates with other applications. 16-bit (sometimes called Legacy) applications lack several features found in their 32-bit counterparts.
Slack Space	The amount of disk space that is wasted by having a large cluster size. For example, if a 300-byte file is stored on a disk with a cluster size of 1,024 bytes, there will be 724 bytes of slack space that can't be used for any other files. You can see how much space is allocated to a file by typing "DIR /v" at the command prompt.
Software	A general term used to describe the programs that can be used on a computer, such as applications, drivers, and operating systems. To the beginner, software is what ever you see on the screen, and hardware is everything you can touch.
Start Menu	The menu that appears when you click the button labelled Start at the bottom of your screen, on the Taskbar.
Swap File	A file on your hard disk called WIN386.SWP that Windows uses to store information when you run out of memory. Since a hard disk is slower than memory, a system without a lot of RAM will run out of memory sooner, requiring heavier use of the swap file, thereby resulting in slower performance. Note that if you've upgraded from Windows 3.x, the old filename for the swap file (386SPART.PAR) is preserved.
Task	Any program that is currently running on your computer. You can switch between tasks with the Taskbar or by pressing Alt-Tab on the keyboard.
Taskbar	The bar along the bottom of your screen, containing the Start Menu and a button for each running Task.
Telnet	A method of connecting to other computers on the Internet. You need a Telnet client (software), and an appropriate account to use Telnet. Windows comes with a simple telnet client, TELNET.EXE.
32-Bit	In reference to Windows applications, a method by which an application uses your computer's memory and communicates with other applications. 32-bit applications typically embody several features not found in their 16-bit counterparts, such as long filenames, preemtive multitasking, and multithreading.
Titlebar	The stripe across the top of a window containing the title of the application in the window. You can move a window by dragging its titlebar.
Tray	The small indented area on your Taskbar that holds the clock by default.
Tree	A graphical diagram used to display the hierarchal structure of the directories on a disk. The Windows Explorer allows the disk to be viewed in this fashion.
Unix	The primary operating system used on the Internet. It is the networking counterpart to DOS, as it also is based upon a command prompt.
User Interface	The Interface to your computer - a combination of controls used to perform any operation. See graphical user interface and command prompt.
WAN	Wide Area Network - a network with all its computers geographically far apart - the Internet is the ultimate WAN.
Window	A rectangular box containing an application, a part of an application, a message, or a folder. This concept is the basis for the user interface in Windows.
Winsock	Short for Windows Sockets - this is the language your computer speaks when it's connected to the Internet. Dial-Up Networking is the winsock support built into Windows. Once you've connected Windows to the internet, you can use winsock clients (software).
Winsock Client	See Client (software).
Workgroup	A type of LAN. The computers that make up a workgroup tend to share the responsibilities equally, as opposed to a client / server relationship.
World Wide Web	The portion of the Internet you used to access this page. WWW for short, it is a subset of the Internet. Netscape, Mozilla, and Internet Explorer are examples of browsers used to navigate the World Wide Web.

More Tech Glossary
anti-virus scanner: Software that scans your computer for viruses, worms, and other malicious software, usually using pattern matching and heuristic algorithms. Pattern-matching involves comparing data in your files to a database of all known viruses. Heuristic algorithms attempt to find files on your computer containing code that does illicit operations, in order to find undiscovered viruses. The latter form of virus scanning is still imperfect, so new viruses often go undetected until scanning software is updated.
apache: Open-source web server software originally for Linux systems but now freely available for numerous platforms. See the Apache.Org website for more information.
BBS: Acronym for Bulletin Board System, a BBS is a computer service where users can chat, post messages, download files, etc. Most BBS's are dial-in. While very popular in the 1980s, the advent of the internet has led to their gradual extinction.
bot: Short for "robot", an automated program usually coded in C for use on IRC.
buffer: A segment of memory assigned by programs to store data.
buffer overflow: The most common security hole, frequently exploited by hackers. It occurs when more data is sent to an input buffer than it can hold. For properly-coded programs that are compiled with memory protection or check for overflow character-by-character, this is not a problem. However, vulnerable programs frequently crash upon buffer overflows. Exploit code left on the memory stack is subsequently executed under the program's process ID. In other words, the hacker can hijack the permissions of the program and use them to execute new commands.
CGI: Acronym for Common Gateway Interface, a protocol that allows for communication between a program and forms on the Web. CGIs are frequently written in C, Perl, or shell scripts, and are used for a variety of form-processing applications. Insecure CGI's are often exploited by web hackers to run illicit commands on a server.
cookies: Cookies are small files that web sites you visit can place on your computer. They are used to track your viewing habits, and often any personal information you provide to the site through forms or other registration processes.
compiler: Program involved in the first step of converting source code writen in a high level language such as C++ to an executable program. Compilers translate the instructions into object code, which is passed on to a linker.
checksum: A value generated by applying some sort of mathematical function to a file. If even a single bit of the file changes, the checksum this function generates should be completely different. Checksums are used to verify the integrity of a file when it is being exchanged over insecure networks.
cron: A UNIX service used to automate tasks, such as daily backups.
cross-site scripting: A security vulnerability in a web application that results from improper filtering of input used to generate some sort of web page (in a form, for example). If the input contains a script which is not stripped out by the web application, it could be processed as part of the output and execute within the domain of the hosting web site. A hostile third-party could 'inject' a malicious script which would run in the user's browser under the security context of the trusted web site. This is frequently exploited to gain access to a user's cookies.
cryptography: Cryptography is the science of transforming data into an unintelligible format (encryption) which can later be restored to its original, readable form (decryption).
daemon: Pronounced "demon." A program that extends the functionality of the operating system, running in the background and working when needed. Web servers, mail servers, print spoolers, etc. are all examples. Also called a service.
DNS: Acronym for Domain Name Service, the system that translates human-readable addresses (such as www.yahoo.com) to IP addresses, and vice-versa.
Denial of Service: Often abbreviated "DoS" - a form of attack intended to disrupt or halt a server's functionality, usually by flooding it with massive amounts of data.
exploit: A program released to demonstrate a security bug.
finger: A UNIX service that provides information about a system's users. Fingering user@host often displays the individual's .plan file. Some hosts will display the users currently logged in upon receiving a finger request in the form of @host. (no username specified)
firewall: A software or hardware-based filter that controls access to internal networks by restricting/allowing certain packets from external hosts.
flooding: A common Denial of Service attack, in which a large amount of data is continually streamed to a single port of a system. The victim computer may slow down or even crash due to the excessive processing overhead.
format string: A vulnerability similar to a format string attacks for more details.
FTP: Acronym for "File Transfer Protocol." A client/server TCP/IP service for transferring files between two computers. Usually runs on port 21.
HTTP: Acronym for "Hypertext Transfer Protocol." A client-server TCP/IP protocol used on the web. Usually runs on port 80.
ICMP: Acronym for Internet Control Message Protocol, a TCP/IP protocol used for sending error and control messages. Ping sents out ICMP echo requests.
IDS: Abbreviation for Intrusion Detection System. Software used to detect and intercept various forms of online attacks.
IIS: Acronym for "Internet Information Server" - Microsoft's line of web server software.
IRC: Acronym for Internet Relay Chat, a popular service that allows users to talk with one another in individual rooms called channels.
kerberos: A network authentication system which provides users or services with tickets and keys used to prove identity and encrypt data streams (to prevent sniffing.)
kernel: The core of an operating system, which always stays in memory and is loaded first. It is responsible for allocating memory, process and disk management, and other functions.
LAN: Acronym for Local Area Network, a set of computers physically linked together to share data or devices.
Linux: A freely distributable implementation of UNIX that runs on many platforms.
mail bomb: A massive amount of e-mail sent to a single person, in an attempt to overload their system. A form of Denial of Service, as networks can become extremely clogged due to the flood of data.
NetBIOS: A protocol Windows PCs use for file and printer sharing on local networks.
NUA: Acronym for Network User Address, address for reaching a particular system via telenet.
PERL: Acronym for Practical Extraction and Report Language, a powerful interpretive language used primarily for text processing on UNIX systems. Perl is the most popular language for writing CGI scripts.
PGP: Acronym for Pretty Good Privacy, a public key cryptography system developed by Philip Zimmerman. It is free, and frequently used to encrypt e-mail.
ping: A program used to test if a server is functional and determine the network latency between two hosts. Ping sends out ICMP packets and waits for responses ("pong").
port: : A software-implemented channel used for network communications. Each server application has a unique port number associated with it. For example, web servers usually are bound to port 80
port scan: Systematically enumerating the open ports on a computer system to determine active services.
public-key cryptography: A form of cryptography which uses two keys - a private key and a public key. Anything encrypted with your public key can only be decrypted with your private key. So you can distribute your public key to anyone in the world, because it only is useful for encrypting data intended for you. The private key, on the other hand, must be kept secured. This form of crypto is used frequently for encrypting e-mail because you don't need a secure mechanism for exchanging the public key. Even if someone intercepts it, without your private key they won't be able to decrypt any of the messages intended for you.
root: User in UNIX systems with superuser power, typically the owner of the machine.
sendmail: A mail-transport program based on SMTP, it is the agent that stores and forwards messages.
service: See daemon.
shell: The outermost layer of a program that provides an interface for users to issue commands. UNIX has multiple shells, including Bash, C shell, and Korn.
SMTP: Acronym for Simple Mail Transfer Protocol, a TCP/IP protocol for sending e-mail. See sendmail.
sniffer: A program which collects/displays all data packets passing through an ethernet device on a LAN. Sniffing is accomplished by setting the device to promiscuous mode, which enables it to listen to all packets, not just the ones destined for it.
spam: Unsolicited commercial e-mail.
spoofing: The process of forging data packets so they appear to come from another host, commonly used to gain access through packet-filtering firewalls and other security systems.
SSH: Acronym for Secure Shell - an alternative to Telnet that uses key-exchange cryptography to secure sessions and defend against sniffing.
SSL: Acronym for Secure Sockets Layer - a "handshake protocol" used to establish a secure HTTP connection with both authentication and encryption. SSL uses public-key cryptography to set up a connection. See the RSA SSL FAQ for more information.
steganography: The science of hiding data in seemingly innocuous formats such as pictures, audio, or video.
SUID: Acronym for Set User Identifier, a designation for UNIX programs that need the privleges of root when executing. Because they have superuser access rights, SUID programs are the most common targets of exploits.
symmetric-key cryptography: A form of cryptography that involves the use of a single key to both encrypt and decrypt data. This key is frequently based on a password phrase. The only key that can decrypt ciphertext (encrypted data) is the same one used to encrypt it - thus it is important that anyone who needs to decrypt your information gets the key over a secure communications medium.
SYN/ACK: Signals used in the "three-way handshake" that establishes a TCP/IP connection between two computers:
1.) Computer A -> SYN -> Computer B ("I want to connect to you, B") 2.) Computer A <- SYN/ACK <- Computer B ("OK, A, I'm here") 3.) Computer A -> ACK -> Computer B ("Acknowledged, B, I'm proceeding") SSL/
telnet: Protocol for connecting to other systems via terminal- like access.
traceroute: Program that shows the pathway packets travel to a destination host by sending ICMP echo requests.
Trojan Horse: A program that seems to be legitimate but actually performs illicit actions when executed. Note that a trojan horse does not necessarily replicate like a virus does.
UDP: User Datagram Protocol, a connectionless TCP service
UID: Acronym for User Identifier, a 16-bit integer that is mapped to a username on UNIX systems. UNIX identifies a user by this number, not the username itself.
UNIX: Acronym for Uniplexed Information and Computing System, a multiuser, multitasking operating system primarily used on workstations and servers. Most internet servers run some variant of UNIX.
UUCP: Acronym for UNIX to UNIX CoPy, an old service used to directly transfer files from one computer to another. It was mostly utilized for mail transport.
VMS: Acronym for Virtual Memory System, an operating system designed for Digital's 32-bit VAX (Virtual Address eXtension) computers. Like UNIX, it is frequently used in server and workstation applications.
virus: A program which illicitly copies itself into memory and other programs, replicating and possibly deleting files or causing some other harm. Infected programs transferred from one system to another spread the virus further.
wardialer: Program which dials a series of numbers within a phone exchange (for example, 555-55XX) to locate modem-connected systems.
warez: Pirated software, illegally downloaded and distributed.
whois: Internet utility used to query a host to find out what users are registered on that system.
worm: A program which illicitly propagates itself on a local system and network, consuming disk space, bandwidth, and other resources. The line between worms and viruses is often blurred - if a malicious program does nothing but try to copy and spread itself then it usually is referred to as a worm instead of a virus.
wrapper: A program used to control access to a second program on UNIX systems, enabled for security reasons.