Glossary M
- MOU/A
- Multipurpose Internet Mail ...
- Mail Server
- Malware
- Masquerading
- Maximum Tolerable Downtime
- Media Access Control
- Media Access Control ...
- Media Sanitization
- Message Digest
- Metacharacter
- Metadata
- Misconfiguration
- MITM Attack
- Mission Critical
- Mobile Device
- Mobile Code
- Most Significant Bit(s)
- Multi-level Security (MLS)

Multipurpose Internet Mail Extensions (MIME)
A protocol that makes use of the headers in an IETF RFC 2822 message to describe the structure of rich message content.See NIST SP 800-45 ...
Mail Server
A host that provides “electronic post office” facilities. It stores incoming mail for distribution to users and forwards outgoing mail. The term may refer to ...
Masquerading
A type of threat action whereby an unauthorized entity gains access to a system or performs a malicious act by illegitimately posing as an authorized ...
Maximum Tolerable Downtime
The amount of time mission/business process can be disrupted without causing significant harm to the organization’s mission. See NIST SP 800-34 Rev. 1 for more information.
Media Access Control
Message Authentication Code. See the following for more information: NIST SP 800-108. NIST SP 800-185. NIST SP 800-56C. An access control policy that is uniformly enforced across all subjects and ...
Media Access Control Address
A hardware address that uniquely identifies each component of an IEEE 802-based network. On networks that do not conform to the IEEE 802 standards but ...
Media Sanitization
A general term referring to the actions taken to render data written on media unrecoverable by both ordinary and extraordinary means. See NIST SP 800-88 Rev. 1 under ...
Message Digest
The result of applying a cryptographic hash function to data (e.g., a message). Also known as a “message digest”. See the following for more information: NIST SP ...
Metacharacter
A character that has some special meaning to a computer program and therefore will not be interpreted properly as part of a literal string.See NISTIR ...
Misconfiguration
An incorrect or suboptimal configuration of an information system or system component that may lead to vulnerabilities.See NIST SP 800-128 under Misconfiguration for detailed information.A ...
MITM Attack
Man in the Middle.An attack using active interception or eavesdropping. It uses a third computer to capture traffic sent between two other systems. See POODLE ...
Mission Critical
Any telecommunications or information system that is defined as a national security system (FISMA) or processes any information the loss, misuse, disclosure, or unauthorized access ...
Mobile Device
A portable computing device that: (i) has a small form factor such that it can easily be carried by a single individual; (ii) is designed ...
Mobile Code
Software programs or parts of programs obtained from remote systems, transmitted across a network, and executed on a local system without explicit installation or execution ...
Most Significant Bit(s)
The left-most bit(s) of a bit string.See the following under Most Significant Bit(s) for detailed information:NIST SP 800-38A.NIST SP 800-38B.NIST SP 800-38C.NIST SP 800-38D.NIST SP ...