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14 M

machine account: An account associated with individual client or server machines in an Active Directory domain.

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.

machine Group Policy object (GPO) version: A version number of the changes for the computer policy portion of a Group Policy object (GPO). This is a 16-bit integer encoded in the lower 16 bits of a GPO version.

MachineID: A unique identifier that represents the identity of a computer.

machine identifier: A GUID that is unique for each machine.


  1. A mechanism for one-way interprocess communications (IPC). For more information, see [MSLOT] and [MS-MAIL].
  2. Within the NetBIOS protocol, refers to the datagram style of communication.

mailslot class: An indication of the expected service of the mailslot. Class 1 is guaranteed delivery, and class 2 is not guaranteed delivery.

main mode (MM): The first phase of an Internet Key Exchange (IKE) negotiation that performs authentication and negotiates a main mode security association (MM SA) between the peers. For more information, see [RFC2409] section 5.

main mode security association (MM SA): A security association used to protect Internet Key Exchange (IKE) traffic between two peers. For more information, see [RFC2408] section 2.

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.

mandatory type-length-value: An attribute that is required in an statement of health (SoH) or statement of health response (SoHR) message in order for that message to be valid and complete.

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).

marshaling: The act of formatting COM parameters for transmission over a remote procedure call (RPC). For more information, see [MS-DCOM].

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.

MD5 hash: A hashing algorithm, as specified in [RFC1321], that was developed by RSA Data Security, Inc. An MD5 hash is used by File Replication Service (FRS) to verify that a file on each replica member is identical.

member (DFS-R): In the Distributed File System Replication Protocol, a computer participating in replication.

member server: A server joined to a domain and that is not acting as an Active Directory domain services domain controller (DC).

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 digest 4 (MD4): As specified in [RFC1320], a collision-resistant, non-rolling hash function that produces a 16-byte hash. While MD4 is no longer considered to be cryptographically secure, remote differential compression (RDC) does not rely on cryptographic security in its 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 Interface Definition Language (MIDL): The Microsoft implementation and extension of OSF-DCE Interface Definition Language (IDL). MIDL can also mean the Interface Definition Language (IDL) compiler provided by Microsoft. For more information, see [MS-RPCE].

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 mode: A state of an Active Directory domain that supports domain controllers (DCs) running Windows NT Server 4.0. Mixed mode does not allow organizations to take advantage of new Active Directory features such as universal groups, nested group membership, and inter-domain group membership.

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:.

MSZIP compression algorithm: The compression algorithm implementing RFC 1591 that is used between Windows 2000 domain controllers (DCs). For more information, see [RFC1591].

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.

multiplexed request: A request where client Server Message Block (SMB) requests from various applications and users are all sent over the same SMB transport connection.

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.

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