L <- 4. Definitions -> N
M
$ MAC
(N) See: mandatory access control, Message Authentication Code.
Deprecated Usage: IDOCs that use this term SHOULD state a
definition for it because this abbreviation is ambiguous.
$ magnetic remanence
(N) Magnetic representation of residual information remaining on a
magnetic medium after the medium has been cleared. [NCS25] (See:
clear, degauss, purge.)
$ main mode
(I) See: /IKE/ under "mode".
$ maintenance hook
(N) "Special instructions (trapdoors) in software allowing easy
maintenance and additional feature development. Since maintenance
hooks frequently allow entry into the code without the usual
checks, they are a serious security risk if they are not removed
prior to live implementation." [C4009] (See: back door.)
$ malicious logic
(I) Hardware, firmware, or software that is intentionally included
or inserted in a system for a harmful purpose. (See: logic bomb,
Trojan horse, spyware, virus, worm. Compare: secondary definitions
under "corruption", "incapacitation", "masquerade", and "misuse".)
$ malware
(D) A contraction of "malicious software". (See: malicious logic.)
Deprecated Term: IDOCs SHOULD NOT use this term; it is not listed
in most dictionaries and could confuse international readers.
$ MAN
(I) metropolitan area network.
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$ man-in-the-middle attack
(I) A form of active wiretapping attack in which the attacker
intercepts and selectively modifies communicated data to
masquerade as one or more of the entities involved in a
communication association. (See: hijack attack, piggyback attack.)
Tutorial: For example, suppose Alice and Bob try to establish a
session key by using the Diffie-Hellman-Merkle algorithm without
data origin authentication service. A "man in the middle" could
(a) block direct communication between Alice and Bob and then (b)
masquerade as Alice sending data to Bob, (c) masquerade as Bob
sending data to Alice, (d) establish separate session keys with
each of them, and (e) function as a clandestine proxy server
between them to capture or modify sensitive information that Alice
and Bob think they are sending only to each other.
$ manager
(I) A person who controls the service configuration of a system or
the functional privileges of operators and other users. (See:
administrative security. Compare: operator, SSO, user.)
$ mandatory access control
1. (I) An access control service that enforces a security policy
based on comparing (a) security labels, which indicate how
sensitive or critical system resources are, with (b) security
clearances, which indicate that system entities are eligible to
access certain resources. (See: discretionary access control, MAC,
rule-based security policy.)
Derivation: This kind of access control is called "mandatory"
because an entity that has clearance to access a resource is not
permitted, just by its own volition, to enable another entity to
access that resource.
2. (O) "A means of restricting access to objects based on the
sensitivity (as represented by a label) of the information
contained in the objects and the formal authorization (i.e.,
clearance) of subjects to access information of such sensitivity."
[DoD1]
$ manipulation detection code
(D) Synonym for "checksum".
Deprecated Term: IDOCs SHOULD NOT use this term as a synonym for
"checksum"; the word "manipulation" implies protection against
active attacks, which an ordinary checksum might not provide.
Instead, if such protection is intended, use "protected checksum"
or some particular type thereof, depending on which is meant. If
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RFC 4949 Internet Security Glossary, Version 2 August 2007
such protection is not intended, use "error detection code" or
some specific type of checksum that is not protected.
$ marking
See: time stamp, security marking.
$ MARS
(O) A symmetric, 128-bit block cipher with variable key length
(128 to 448 bits), developed by IBM as a candidate for the AES.
$ Martian
(D) /slang/ A packet that arrives unexpectedly at the wrong
address or on the wrong network because of incorrect routing or
because it has a non-registered or ill-formed IP address. [R1208]
Deprecated Term: It is likely that other cultures use different
metaphors for this concept. Therefore, to avoid international
misunderstanding, IDOCs SHOULD NOT use this term. (See: Deprecated
Usage under "Green Book".)
$ masquerade
(I) 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 entity. (See: deception.)
Usage: This type of threat action includes the following subtypes:
- "Spoof": Attempt by an unauthorized entity to gain access to a
system by posing as an authorized user.
- "Malicious logic": In context of masquerade, any hardware,
firmware, or software (e.g., Trojan horse) that appears to
perform a useful or desirable function, but actually gains
unauthorized access to system resources or tricks a user into
executing other malicious logic. (See: corruption,
incapacitation, main entry for "malicious logic", misuse.)
$ MCA
(O) See: merchant certification authority.
$ MD2
(N) A cryptographic hash [R1319] that produces a 128-bit hash
result, was designed by Ron Rivest, and is similar to MD4 and MD5
but slower.
Derivation: Apparently, an abbreviation of "message digest", but
that term is deprecated by this Glossary.
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$ MD4
(N) A cryptographic hash [R1320] that produces a 128-bit hash
result and was designed by Ron Rivest. (See: Derivation under
"MD2", SHA-1.)
$ MD5
(N) A cryptographic hash [R1321] that produces a 128-bit hash
result and was designed by Ron Rivest to be an improved version of
MD4. (See: Derivation under "MD2".)
$ merchant
(O) /SET/ "A seller of goods, services, and/or other information
who accepts payment for these items electronically." [SET2] A
merchant may also provide electronic selling services and/or
electronic delivery of items for sale. With SET, the merchant can
offer its cardholders secure electronic interactions, but a
merchant that accepts payment cards is required to have a
relationship with an acquirer. [SET1, SET2]
$ merchant certificate
(O) /SET/ A public-key certificate issued to a merchant. Sometimes
used to refer to a pair of such certificates where one is for
digital signature use and the other is for encryption.
$ merchant certification authority (MCA)
(O) /SET/ A CA that issues digital certificates to merchants and
is operated on behalf of a payment card brand, an acquirer, or
another party according to brand rules. Acquirers verify and
approve requests for merchant certificates prior to issuance by
the MCA. An MCA does not issue a CRL, but does distribute CRLs
issued by root CAs, brand CAs, geopolitical CAs, and payment
gateway CAs. [SET2]
$ mesh PKI
(I) A non-hierarchical PKI architecture in which there are several
trusted CAs rather than a single root. Each certificate user bases
path validations on the public key of one of the trusted CAs,
usually the one that issued that user's own public-key
certificate. Rather than having superior-to-subordinate
relationships between CAs, the relationships are peer-to-peer, and
CAs issue cross-certificates to each other. (Compare: hierarchical
PKI, trust-file PKI.)
$ Message Authentication Code (MAC), message authentication code
1. (N) /capitalized/ A specific ANSI standard for a checksum that
is computed with a keyed hash that is based on DES. [A9009] Usage:
a.k.a. Data Authentication Code, which is a U.S. Government
standard. [FP113] (See: MAC.)
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RFC 4949 Internet Security Glossary, Version 2 August 2007
2. (D) /not capitalized/ Synonym for "error detection code".
Deprecated Term: IDOCs SHOULD NOT use the uncapitalized form
"message authentication code". Instead, use "checksum", "error
detection code", "hash", "keyed hash", "Message Authentication
Code", or "protected checksum", depending on what is meant. (See:
authentication code.)
The uncapitalized form mixes concepts in a potentially misleading
way. The word "message" is misleading because it implies that the
mechanism is particularly suitable for or limited to electronic
mail (see: Message Handling Systems). The word "authentication" is
misleading because the mechanism primarily serves a data integrity
function rather than an authentication function. The word "code"
is misleading because it implies that either encoding or
encryption is involved or that the term refers to computer
software.
$ message digest
(D) Synonym for "hash result". (See: cryptographic hash.)
Deprecated Term: IDOCs SHOULD NOT use this term as a synonym for
"hash result"; this term unnecessarily duplicates the meaning of
the other, more general term and mixes concepts in a potentially
misleading way. The word "message" is misleading because it
implies that the mechanism is particularly suitable for or limited
to electronic mail (see: Message Handling Systems).
$ message handling system
(D) Synonym for the Internet electronic mail system.
Deprecated Term: IDOCs SHOULD NOT use this term, because it could
be confused with Message Handling System. Instead, use "Internet
electronic mail" or some other, more specific term.
$ Message Handling System
(O) An ITU-T system concept that encompasses the notion of
electronic mail but defines more comprehensive OSI systems and
services that enable users to exchange messages on a store-and-
forward basis. (The ISO equivalent is "Message Oriented Text
Interchange System".) (See: X.400.)
$ message indicator
1. (D) /cryptographic function/ Synonym for "initialization
value". (Compare: indicator.)
2. (D) "Sequence of bits transmitted over a communications system
for synchronizing cryptographic equipment." [C4009]
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RFC 4949 Internet Security Glossary, Version 2 August 2007
Deprecated Term: IDOCs SHOULD NOT use this term as a synonym for
"initialization value"; the term mixes concepts in a potentially
misleading way. The word "message" is misleading because it
suggests that the mechanism is specific to electronic mail. (See:
Message Handling System.)
$ message integrity check
$ message integrity code (MIC)
(D) Synonyms for some form of "checksum".
Deprecated Term: IDOCs SHOULD NOT use these terms for any form of
checksum. Instead, use "checksum", "error detection code", "hash",
"keyed hash", "Message Authentication Code", or "protected
checksum", depending on what is meant.
These two terms mix concepts in potentially misleading ways. The
word "message" is misleading because it suggests that the
mechanism is particularly suitable for or limited to electronic
mail. The word "integrity" is misleading because the checksum may
be used to perform a data origin authentication function rather
than an integrity function. The word "code" is misleading because
it suggests either that encoding or encryption is involved or that
the term refers to computer software.
$ Message Security Protocol (MSP)
(N) A secure message handling protocol [SDNS7] for use with X.400
and Internet mail protocols. Developed by NSA's SDNS program and
used in the U.S. DoD's Defense Message System.
$ meta-data
(I) Descriptive information about a data object; i.e., data about
data, or data labels that describe other data. (See: security
label. Compare: metadata)
Tutorial: Meta-data can serve various management purposes:
- System management: File name, type, size, creation date.
- Application management: Document title, version, author.
- Usage management: Data categories, keywords, classifications.
Meta-data can be associated with a data object in two basic ways:
- Explicitly: Be part of the data object (e.g., a header field of
a data file or packet) or be linked to the object.
- Implicitly: Be associated with the data object because of some
other, explicit attribute of the object.
$ metadata, Metadata(trademark), METADATA(trademark)
(D) Proprietary variants of "meta-data". (See: SPAM(trademark).)
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RFC 4949 Internet Security Glossary, Version 2 August 2007
Deprecated Usage: IDOCs SHOULD NOT use these unhypenated forms;
IDOCs SHOULD use only the uncapitalized, hyphenated "meta-data".
The terms "Metadata" and "METADATA" are claimed as registered
trademarks (numbers 1,409,260 and 2,185,504) owned by The Metadata
Company, originally known as Metadata Information Partners, a
company founded by Jack Myers. The status of "metadata" is
unclear.
$ MHS
(N) See: message handling system.
$ MIC
(D) See: message integrity code.
$ MIME
(I) See: Multipurpose Internet Mail Extensions.
$ MIME Object Security Services (MOSS)
(I) An Internet protocol [R1848] that applies end-to-end
encryption and digital signature to MIME message content, using
symmetric cryptography for encryption and asymmetric cryptography
for key distribution and signature. MOSS is based on features and
specifications of PEM. (See: S/MIME.)
$ Minimum Interoperability Specification for PKI Components (MISPC)
(N) A technical description to provide a basis for interoperation
between PKI components from different vendors; consists primarily
of a profile of certificate and CRL extensions and a set of
transactions for PKI operation. [SP15]
$ misappropriation
(I) A type of threat action whereby an entity assumes unauthorized
logical or physical control of a system resource. (See:
usurpation.)
Usage: This type of threat action includes the following subtypes:
- Theft of data: Unauthorized acquisition and use of data
contained in a system.
- Theft of service: Unauthorized use of a system service.
- Theft of functionality: Unauthorized acquisition of actual
hardware, firmware, or software of a system component.
$ MISPC
(N) See: Minimum Interoperability Specification for PKI
Components.
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$ MISSI
(O) Multilevel Information System Security Initiative, an NSA
program to encourage development of interoperable, modular
products for constructing secure network information systems in
support of a wide variety of U.S. Government missions. (See: MSP,
SP3, SP4.)
$ MISSI user
(O) /MISSI/ A system entity that is the subject of one or more
MISSI X.509 public-key certificates issued under a MISSI
certification hierarchy. (See: personality.)
Tutorial: MISSI users include both end users and the authorities
that issue certificates. A MISSI user is usually a person but may
be a machine or other automated process. Machines that are
required to operate nonstop may be issued their own certificates
to avoid downtime needed to exchange the FORTEZZA cards of machine
operators at shift changes.
$ mission
(I) A statement of a (relatively long-term) duty or (relatively
short-term) task that is assigned to an organization or system,
indicates the purpose and objectives of the duty or task, and may
indicate the actions to be taken to achieve it.
$ mission critical
(I) A condition of a system service or other system resource such
that denial of access to, or lack of availability of, the resource
would jeopardize a system user's ability to perform a primary
mission function or would result in other serious consequences.
(See: Critical. Compare: mission essential.)
$ mission essential
(O) /U.S. DoD/ Refers to materiel that is authorized and available
to combat, combat support, combat service support, and combat
readiness training forces to accomplish their assigned missions.
[JP1] (Compare: mission critical.)
$ misuse
1. (I) The intentional use (by authorized users) of system
resources for other than authorized purposes. Example: An
authorized system administrator creates an unauthorized account
for a friend. (See: misuse detection.)
2. (I) A type of threat action that causes a system component to
perform a function or service that is detrimental to system
security. (See: usurpation.)
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Usage: This type of threat action includes the following subtypes:
- "Tampering": /misuse/ Deliberately altering a system's logic,
data, or control information to cause the system to perform
unauthorized functions or services. (See: corruption, main
entry for "tampering".)
- "Malicious logic": /misuse/ Any hardware, firmware, or software
intentionally introduced into a system to perform or control
execution of an unauthorized function or service. (See:
corruption, incapacitation, main entry for "malicious logic",
masquerade.)
- "Violation of authorizations": Action by an entity that exceeds
the entity's system privileges by executing an unauthorized
function. (See: authorization.)
$ misuse detection
(I) An intrusion detection method that is based on rules that
specify system events, sequences of events, or observable
properties of a system that are believed to be symptomatic of
security incidents. (See: IDS, misuse. Compare: anomaly
detection.)
$ MLS
(I) See: multilevel secure
$ mobile code
1a. (I) Software that originates from a remote server, is
transmitted across a network, and is loaded onto and executed on a
local client system without explicit initiation by the client's
user and, in some cases, without that user's knowledge. (Compare:
active content.)
Tutorial: One form of mobile code is active content in a file that
is transferred across a network.
1b. (O) /U.S. DoD/ "Software modules obtained from remote systems,
transferred across a network, and then downloaded and executed on
local systems without explicit installation or execution by the
recipient." [JP1]
2a. (O) /U.S. DoD/ Technology that enables the creation of
executable information that can be delivered to an information
system and directly executed on any hardware/software architecture
that has an appropriate host execution environment.
2b. (O) "Programs (e.g., script, macro, or other portable
instruction) that can be shipped unchanged to a heterogeneous
collection of platforms and executed with identical semantics"
[SP28]. (See: active content.)
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Tutorial: Mobile code might be malicious. Using techniques such as
"code signing" and a "sandbox" can reduce the risks of receiving
and executing mobile code.
$ mode
$ mode of operation
1. (I) /cryptographic operation/ A technique for enhancing the
effect of a cryptographic algorithm or adapting the algorithm for
an application, such as applying a block cipher to a sequence of
data blocks or a data stream. (See: CBC, CCM, CMAC, CFB, CTR, ECB,
OFB.)
2. (I) /system operation/ A type of security policy that states
the range of classification levels of information that a system is
permitted to handle and the range of clearances and authorizations
of users who are permitted to access the system. (See:
compartmented security mode, controlled security mode, dedicated
security mode, multilevel security mode, partitioned security
mode, system-high security mode. Compare: protection level.)
3. (I) /IKE/ IKE refers to its various types of ISAKMP-scripted
exchanges of messages as "modes". Among these are the following:
- "Main mode": One of IKE's two phase 1 modes. (See: ISAKMP.)
- "Quick mode": IKE's only phase 2 mode. (See: ISAKMP.)
$ model
See: formal model, security model.
$ modulus
(I) The defining constant in modular arithmetic, and usually a
part of the public key in asymmetric cryptography that is based on
modular arithmetic. (See: Diffie-Hellman-Merkle, RSA.)
$ Mondex
(O) A smartcard-based electronic money system that incorporates
cryptography and can be used to make payments via the Internet.
(See: IOTP.)
$ Morris Worm
(I) A worm program that flooded the ARPANET in November 1988,
causing problems for thousands of hosts. [R1135] (See: community
risk, worm)
$ MOSS
(I) See: MIME Object Security Services.
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$ MQV
(N) A key-agreement protocol [Mene] that was proposed by A.J.
Menezes, M. Qu, and S.A. Vanstone in 1995 and is based on the
Diffie-Hellman-Merkle algorithm.
$ MSP
(N) See: Message Security Protocol.
$ multicast security
See: secure multicast
$ Multics
(N) MULTiplexed Information and Computing Service, an MLS computer
timesharing system designed and implemented during 1965-69 by a
consortium including Massachusetts Institute of Technology,
General Electric, and Bell Laboratories, and later offered
commercially by Honeywell.
Tutorial: Multics was one of the first large, general-purpose,
operating systems to include security as a primary goal from the
inception of the design and development and was rated in TCSEC
Class B2. Its many innovative hardware and software security
mechanisms (e.g., protection ring) were adopted by later systems.
$ multilevel secure (MLS)
(I) Describes an information system that is trusted to contain,
and maintain separation between, resources (particularly stored
data) of different security levels. (Examples: BLACKER, CANEWARE,
KSOS, Multics, SCOMP.)
Usage: Usually understood to mean that the system permits
concurrent access by users who differ in their access
authorizations, while denying users access to resources for which
they lack authorization.
$ multilevel security mode
1. (N) A mode of system operation wherein (a) two or more security
levels of information are allowed to be to be handled concurrently
within the same system when some users having access to the system
have neither a security clearance nor need-to-know for some of the
data handled by the system and (b) separation of the users and the
classified material on the basis, respectively, of clearance and
classification level are dependent on operating system control.
(See: /system operation/ under "mode", need to know, protection
level, security clearance. Compare: controlled mode.)
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Usage: Usually abbreviated as "multilevel mode". This term was
defined in U.S. Government policy regarding system accreditation,
but the term is also used outside the Government.
2. (O) A mode of system operation in which all three of the
following statements are true: (a) Some authorized users do not
have a security clearance for all the information handled in the
system. (b) All authorized users have the proper security
clearance and appropriate specific access approval for the
information to which they have access. (c) All authorized users
have a need-to-know only for information to which they have
access. [C4009] (See: formal access approval, protection level.)
$ Multipurpose Internet Mail Extensions (MIME)
(I) An Internet protocol (RFC 2045) that enhances the basic format
of Internet electronic mail messages (RFC 822) (a) to enable
character sets other than U.S. ASCII to be used for textual
headers and content and (b) to carry non-textual and multi-part
content. (See: S/MIME.)
$ mutual suspicion
(I) The state that exists between two interacting system entities
in which neither entity can trust the other to function correctly
with regard to some security requirement.
L <- 4. Definitions -> N