machine connection: A connection to a printer (shared from a print server) on a client machine. A connection is displayed in the user interface as a printer. Machine connections are displayed for all users (in all user environments) of a particular client machine.
MachineID: A unique identifier that represents the identity of a computer.
machine identifier: A GUID that is unique for each machine.
mailslot class: An indication of the expected service of the mailslot. Class 1 is guaranteed delivery, and class 2 is not guaranteed delivery.
main stream: The place within a file where data is stored or the data stored therein. A main stream has no name. The main stream is what is ordinarily thought of as the contents of a file.
manageable entity: A Common Information Model (CIM) instance representing a manageable component of an operating system.
Managed Object Format (MOF): A textual encoding for Common Information Model (CIM) objects called managed object format (MOF), this representation is not used within protocol operations defined in [MS-WMI]. MOF is defined in [DMTF-DSP004] section 3. The MOF text encoding is only used for illustrative purposes. The binary encoding in this specification can be translated to and from the MOF format.
man in the middle (MITM): An attack that deceives a server or client into accepting an unauthorized upstream host as the actual legitimate host. Instead, the upstream host is an attacker's host that is manipulating the network so the attacker's host appears to be the desired destination. This enables the attacker to decrypt and access all network traffic that would go to the legitimate host.
marshal: To encode one or more data structures into an octet stream using a specific remote procedure call (RPC) transfer syntax (for example, marshaling a 32-bit integer).
masked disk: A disk that is invisible to the local machine, even though a physical connection exists between the disk and the machine.
mass storage device: Any hardware device that provides persistent storage of data.
master boot record (MBR): Metadata such as the partition table, the disk signature, and the executable code for initiating the operating system boot process that is located on the first sector of a disk. Disks that have MBRs are referred to as MBR disks. GUID partitioning table (GPT) disks, instead, have unused dummy data in the first sector where the MBR would normally be.
master browser server: A server responsible for maintaining a master list of available resources on a subnet, and for making the list available to backup browser servers. Each subnet requires a master browser server. The master browser server for a particular domain is called the domain master browser server.
master locator: A server that enables querying for server entries exported on a different machine.
master session key: A temporary cryptographic key used to derive other cryptographic keys to be used to encrypt and decrypt parts of session-based protocol.
maximum transmission unit (MTU): The size, in bytes, of the largest packet that a given layer of a communications protocol can pass onward.
member (DFS-R): In the Distributed File System Replication Protocol, a computer participating in replication.
merge disks or disk groups: The act of combining disks in two separate and distinct disk groups to form a single disk group.
message: See message tag (MTAG).
Message Authentication Code (MAC): A message authenticator computed through the use of a symmetric key.
Message Authentication Code protocol data unit (MPDU): The unit of data exchanged between two peer Message Authentication Code (MAC) entities by using the services of the physical layer.
Message Authentication Code sublayer management entity (MLME): An entity that provides the layer management service interfaces through which layer management functions may be invoked.
message digest: See hash function.
message identifier: An index into a message table. A message table is a collection of localizable strings. For Windows implementations, the message table is stored in the resource section of a dynamic link library.
message mode: A Named Pipe can be of two types: byte mode or message mode. In byte mode, the data sent or received on the Named Pipe does not have message boundaries but is treated as a continuous Stream. In Message Mode, message boundaries are enforced.
message server: An remote procedure call (RPC) server that implements this protocol.
message tag (MTAG): A message that is sent between participants in the context of connections.
Messaging Application Programming Interface (MAPI): A Windows programming interface that enables e-mail to be sent from within a Windows application.
metafile: A sequence of record structures that store an image in an application-independent format. Metafile records contain drawing commands, object definitions, and configuration settings. When a metafile is processed, the stored image can be rendered on a display, output to a printer or plotter, stored in memory, or saved to a file or stream.
Microsoft Management Console (MMC): The Microsoft Management Console (MMC) provides a framework that consists of a graphical user interface (GUI) and a programming platform in which snap-ins (collections of administrative tools) can be created, opened, and saved. MMC is a multiple-document interface (MDI) application.
mirrored volume: A fault-tolerant volume that maintains two or more copies of the volume's data. In the event that a disk is lost, at least one copy of the volume's data remains and can be accessed.
mixed proxy: A network node that acts as a proxy for both inbound and outbound traffic between a client and a server.
modification sequence number: An implementation-defined value for objects such as disks, volumes, drive letters, partitions and regions that increases monotonically each time a configuration operation takes place on the object.
most specific object class: The class that none of the other classes inherits from, in a sequence of object classes related by inheritance. The special object class top is less specific than any other class.
mount path: See mounted folder.
mount point: See mounted folder.
mount point access path: See mounted folder.
mounted folder: A file system directory that contains a linked path to a second volume. A user may link a path on one volume to another (for example, given two volumes C: and D:, a user can create a directory or folder C:\mountD and link that directory with volume D:. The path C:\MountD can then be used to access the root folder of volume D:.
multicast: A content delivery method in which a single stream is transmitted from a media server to multiple clients. The clients have no connection with the server. Instead, the server sends a single copy of the stream across the network to multicast-enabled routers, which replicate the data. Clients can then receive the stream by monitoring a specific multicast IP address and port.
multipartition volume: A volume containing data that exists on more than one partition.
multisz: A data type that defines an array of null-terminated, 16-bit Unicode UTF-16LE-encoded strings, with an additional null after the final string.
mutual authentication: A mode in which each party verifies the identity of the other party, as specified in [RFC3748] section 7.2.1.