macro - A single computer instruction that stands for a sequence of operations.

mail bomb - massive amounts of e-mail sent to a single person, with malicious intent to overload the recipient's system. Mail bombing can cause problems not only for the targeted recipient, but also for other users of the networks involved.

mail bomber – software that will flood a victim's inbox with hundreds or thousands of pieces of mail. Such mail generally does not correctly reveal its source.

maillist (or mailing list) - An automated system that allows people to send e-mail to one address, whereupon their message is copied and sent to all of the other subscribers to the maillist.

Majordomo - A UNIX mailing list processor used to manage e-mail discussion lists.

malware - malicious software designed to do harm to a user's system or to other systems. This does not include viruses and worms.

MAPI {MAP-ee} [Mail Application Program Interface] - A programming interface that enables an application to send and receive mail over the Microsoft Mail messaging system.

markup - The process of adding coding to a text document that gives instructions for layout, type styling, placement of graphics, or other information which will be interpreted by the system used to read the document.

markup language - Language that has codes for indicating layout and styling (such as boldface, italics, paragraphs, insertion of graphics, etc.) within a text file; for example HTML.

mass mailer – a virus that distributes itself via e-mail to multiple addressees at once.

master key - symmetric key used by a certificate manager to encrypt information.

master password - password used by a certificate manager to protect the master key and/or private keys stored on a security device.

math coprocessor - (see "floating-point processor")

megabyte [MB] - 1 million bytes (1,048,576 bytes).

megapixel - One-million pixels, a unit of measurement in an image. This number will determine the quality of the image. Megapixel images have a lot of detail and make very large files.

memory - The working space used by the computer to hold the program that is currently running, along with the data it needs, and to run programs and process data. The main memory is built from RAM chips. The amount of memory available determines the size of programs that can be run, and whether more than one program can be run at once. Main memory is temporary, and is lost when the computer is turned off.

memory card - A small electronic device that stores files. With digital photography, it is used to save images. The larger the storage capacity, the more images it holds.

memory resident - Remaining in memory in order to be available for immediate use. (see "TSR")

memory stick (See "flash drive")

menu - A list from which the user may select an operation to be performed. This is often done with a mouse or other pointing device, but may also be controlled from the keyboard.

menu bar - A permanently displayed menu spread horizontally across the top of the screen or window. When the mouse is pressed over an item on the menu, a pull-down menu appears.

metafile - A file format designed for exchanging graphical data between different application programs or different machines, often as a bitmap.

MHz [Megahertz] - Millions of cycles per seconds. The measure of the speed of a computer. A 500-MHz CPU can process data 500 million times a second.

mickey - A unit by which mouse movement is measured: 1/200th of an inch.

microprocessor - A computer whose entire CPU is contained on one or two integrated circuits.

midi {mid-ee} [Musical Instrument Digital Interface] - A standard for encoding musical sounds in digital form. A port that allows a musical instrument to be connected to a computer.

millennium - One thousand years. Because the first year of the first millennium AD was 1 AD rather than 0 AD, the first year of the second millennium was 1001 AD. Therefore, in spite of all the fuss about the Year 2000, the third millennium did not actually start until Jan. 1, 2001.

MIME {mime} [Multipurpose Internet Mail Extensions] - The standard for attaching non-text files to standard Internet mail messages. Non-text files include graphics, spreadsheets, word-processor documents, sound files, etc.

mirror site - A duplicate of a busy archive site, which is maintained in order to reduce the load on the source site and to speed up access for users close to the mirror site.

misrepresentation - Presentation of an entity as a person or organization that it is not. For example, a Web site might pretend to be a furniture store when it is really just a site that takes credit card payments, but never sends any goods. (See also "spoofing")

modem {mo-dem} [modulator/demodulator] - Device that converts the digital signals generated by a computer to the modulated, analog signals required for transmission over telephone lines and transforms incoming analog signals to their digital equivalents. A modem may either be internal or external, connected to one of the computer's serial ports.

modulate - to vary the amplitude, frequency, or phase of a light wave or electronic wave for the transmission of information.

monitor - The computer's display or video system.

monitoring tool - software placed in your computer to record e-mails, chats, instant messaging, Web sites visits, programs run, keystrokes typed, etc. It immediately sends a copy to the subscriber (installer) of the monitoring service.

Mosaic - Browser developed by Marc Andressen at the National Center for Supercomputing Applications (NCSA) at the University of Illinois, Urbana-Champaign in 1993. It provides a stable, graphical interface to the information on the Internet.

motherboard - Main printed circuit board in a computer that is the foundation of the computer system. In personal computers, the motherboard contains the bus, the microprocessor, and chips used for controlling any built-in peripherals such as the keyboard, text and graphics display, serial ports and parallel ports, joystick and mouse interfaces.

mouse - A device about the size of your palm that you roll around on a flat surface to move the computer's cursor.

mouse around - Look around on the Internet or another network.

mouse droppings - Pixels (usually single) that are not properly restored when the mouse pointer moves away from a particular location on the screen, producing the appearance that the mouse pointer has left droppings behind.

mouse pointer - The symbol on the screen that is moved with the mouse. Within text, the mouse pointer appears as a cursor, but it changes shape depending on its location on the screen and the program in use. The pointer can take the form of a hand, an arrow, a cross, and other symbols. Also called a mouse cursor.

mouse trails - A feature which causes the mouse pointer to leave a trail across the screen.

MP3 [Motion Picture Experts Group, Audio Layer 3] - A popular music download format. MP3 produces CD-quality music in a compressed file that can be transferred quickly, and played on any multimedia computer with MP3 player software. The technology creates sound files a tenth the size of standard CD music files with very little loss of sound quality.

MRU - a listing of the Most Recently Used lists stored in your registry. They are harmless and consist only of things such as the most recent document you opened.

MS-DOS (See DOS)

multimedia - Presentation of information on a PC using a combination of sound, graphics, animation and video.

multitasking - Execution of two or more programs at a time on a computer system.

My Computer - In Windows, a desktop folder that contains drive icon's, Printers folder, Dial-up Networking folder, Control Panel and Scheduled Tasks. If you right-click on My Computer, you can view the Properties of Windows, including version, amount of RAM and device configuration.

My Documents - In Windows, a desktop folder that provides you with a convenient place to store documents, graphics, or other files you want to access quickly. On your desktop, it is represented by a folder with a sheet of paper in it. When you save a file in a program such as WordPad or Paint, the file is automatically saved in My Documents unless you choose a different location.