E <- 4. Definitions -> G
F
$ fail-safe
1. (I) Synonym for "fail-secure".
2. (I) A mode of termination of system functions that prevents
damage to specified system resources and system entities (i.e.,
specified data, property, and life) when a failure occurs or is
detected in the system (but the failure still might cause a
security compromise). (See: failure control.)
Tutorial: Definitions 1 and 2 are opposing design alternatives.
Therefore, IDOCs SHOULD NOT use this term without providing a
definition for it. If definition 1 is intended, IDOCs can avoid
ambiguity by using "fail-secure" instead.
$ fail-secure
(I) A mode of termination of system functions that prevents loss
of secure state when a failure occurs or is detected in the system
(but the failure still might cause damage to some system resource
or system entity). (See: failure control. Compare: fail-safe.)
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$ fail-soft
(I) Selective termination of affected, non-essential system
functions when a failure occurs or is detected in the system.
(See: failure control.)
$ failure control
(I) A methodology used to provide fail-safe, fail-secure or fail-
soft termination and recovery of system functions. [FP039]
$ fairness
(I) A property of an access protocol for a system resource whereby
the resource is made equitably or impartially available to all
eligible users. (RFC 3753)
Tutorial: Fairness can be used to defend against some types of
denial-of-service attacks on a system connected to a network.
However, this technique assumes that the system can properly
receive and process inputs from the network. Therefore, the
technique can mitigate flooding but is ineffective against
jamming.
$ falsification
(I) A type of threat action whereby false data deceives an
authorized entity. (See: active wiretapping, deception.)
Usage: This type of threat action includes the following subtypes:
- "Substitution": Altering or replacing valid data with false
data that serves to deceive an authorized entity.
- "Insertion": Introducing false data that serves to deceive an
authorized entity.
$ fault tree
(I) A branching, hierarchical data structure that is used to
represent events and to determine the various combinations of
component failures and human acts that could result in a specified
undesirable system event. (See: attack tree, flaw hypothesis
methodology.)
Tutorial: "Fault-tree analysis" is a technique in which an
undesired state of a system is specified and the system is studied
in the context of its environment and operation to find all
credible ways in which the event could occur. The specified fault
event is represented as the root of the tree. The remainder of the
tree represents AND or OR combinations of subevents, and
sequential combinations of subevents, that could cause the root
event to occur. The main purpose of a fault-tree analysis is to
calculate the probability of the root event, using statistics or
other analytical methods and incorporating actual or predicted
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quantitative reliability and maintainability data. When the root
event is a security violation, and some of the subevents are
deliberate acts intended to achieve the root event, then the fault
tree is an attack tree.
$ FEAL
(O) A family of symmetric block ciphers that was developed in
Japan; uses a 64-bit block, keys of either 64 or 128 bits, and a
variable number of rounds; and has been successfully attacked by
cryptanalysts. [Schn]
$ Federal Information Processing Standards (FIPS)
(N) The Federal Information Processing Standards Publication (FIPS
PUB) series issued by NIST under the provisions of Section 111(d)
of the Federal Property and Administrative Services Act of 1949 as
amended by the Computer Security Act of 1987 (Public Law 100-235)
as technical guidelines for U.S. Government procurements of
information processing system equipment and services. (See:
"[FPxxx]" items in Section 7, Informative References.)
$ Federal Public-key Infrastructure (FPKI)
(O) A PKI being planned to establish facilities, specifications,
and policies needed by the U.S. Government to use public-key
certificates in systems involving unclassified but sensitive
applications and interactions between Federal agencies as well as
with entities of state and local governments, the business
community, and the public. [FPKI]
$ Federal Standard 1027
(N) An U.S. Government document defining emanation, anti-tamper,
security fault analysis, and manual key management criteria for
DES encryption devices, primary for OSIRM Layer 2. Was renamed
"FIPS PUB 140" when responsibility for protecting unclassified,
sensitive information was transferred from NSA to NIST, and has
since been superseded by newer versions of that standard [FP140].
$ File Transfer Protocol (FTP)
(I) A TCP-based, Application-Layer, Internet Standard protocol
(RFC 959) for moving data files from one computer to another.
$ fill device
(N) /COMSEC/ A device used to transfer or store keying material in
electronic form or to insert keying material into cryptographic
equipment.
$ filter
1. (I) /noun/ Synonym for "guard". (Compare: content filter,
filtering router.)
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2. (I) /verb/ To process a flow of data and selectively block
passage or permit passage of individual data items according to a
security policy.
$ filtering router
(I) An internetwork router that selectively prevents the passage
of data packets according to a security policy. (See: guard.)
Tutorial: A router usually has two or more physical connections to
networks or other systems; and when the router receives a packet
on one of those connections, it forwards the packet on a second
connection. A filtering router does the same; but it first
decides, according to some security policy, whether the packet
should be forwarded at all. The policy is implemented by rules
(packet filters) loaded into the router. The rules mostly involve
values of data packet control fields (especially IP source and
destination addresses and TCP port numbers) [R2179]. A filtering
router may be used alone as a simple firewall or be used as a
component of a more complex firewall.
$ financial institution
(N) "An establishment responsible for facilitating customer-
initiated transactions or transmission of funds for the extension
of credit or the custody, loan, exchange, or issuance of money."
[SET2]
$ fingerprint
1. (I) A pattern of curves formed by the ridges on a fingertip.
(See: biometric authentication. Compare: thumbprint.)
2. (D) /PGP/ A hash result ("key fingerprint") used to
authenticate a public key or other data. [PGP]
Deprecated Definition: IDOCs SHOULD NOT use this term with
definition 2, and SHOULD NOT use this term as a synonym for "hash
result" of *any* kind. Either use would mix concepts in a
potentially misleading way.
$ FIPS
(N) See: Federal Information Processing Standards.
$ FIPS PUB 140
(N) The U.S. Government standard [FP140] for security requirements
to be met by a cryptographic module when the module is used to
protect unclassified information in computer and communication
systems. (See: Common Criteria, FIPS, Federal Standard 1027.)
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Tutorial: The standard specifies four increasing levels (from
"Level 1" to "Level 4") of requirements to cover a wide range of
potential applications and environments. The requirements address
basic design and documentation, module interfaces, authorized
roles and services, physical security, software security,
operating system security, key management, cryptographic
algorithms, electromagnetic interference and electromagnetic
compatibility (EMI/EMC), and self-testing. NIST and the Canadian
Communication Security Establishment jointly certify modules.
$ FIREFLY
(O) /U.S. Government/ "Key management protocol based on public-key
cryptography." [C4009]
$ firewall
1. (I) An internetwork gateway that restricts data communication
traffic to and from one of the connected networks (the one said to
be "inside" the firewall) and thus protects that network's system
resources against threats from the other network (the one that is
said to be "outside" the firewall). (See: guard, security
gateway.)
2. (O) A device or system that controls the flow of traffic
between networks using differing security postures. [SP41]
Tutorial: A firewall typically protects a smaller, secure network
(such as a corporate LAN, or even just one host) from a larger
network (such as the Internet). The firewall is installed at the
point where the networks connect, and the firewall applies policy
rules to control traffic that flows in and out of the protected
network.
A firewall is not always a single computer. For example, a
firewall may consist of a pair of filtering routers and one or
more proxy servers running on one or more bastion hosts, all
connected to a small, dedicated LAN (see: buffer zone) between the
two routers. The external router blocks attacks that use IP to
break security (IP address spoofing, source routing, packet
fragments), while proxy servers block attacks that would exploit a
vulnerability in a higher-layer protocol or service. The internal
router blocks traffic from leaving the protected network except
through the proxy servers. The difficult part is defining criteria
by which packets are denied passage through the firewall, because
a firewall not only needs to keep unauthorized traffic (i.e.,
intruders) out, but usually also needs to let authorized traffic
pass both in and out.
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$ firmware
(I) Computer programs and data stored in hardware -- typically in
read-only memory (ROM) or programmable read-only memory (PROM) --
such that the programs and data cannot be dynamically written or
modified during execution of the programs. (See: hardware,
software.)
$ FIRST
(N) See: Forum of Incident Response and Security Teams.
$ flaw
1. (I) An error in the design, implementation, or operation of an
information system. A flaw may result in a vulnerability.
(Compare: vulnerability.)
2. (D) "An error of commission, omission, or oversight in a system
that allows protection mechanisms to be bypassed." [NCSSG]
(Compare: vulnerability. See: brain-damaged.)
Deprecated Definition: IDOCs SHOULD NOT use this term with
definition 2; not every flaw is a vulnerability.
$ flaw hypothesis methodology
(I) An evaluation or attack technique in which specifications and
documentation for a system are analyzed to hypothesize flaws in
the system. The list of hypothetical flaws is prioritized on the
basis of the estimated probability that a flaw exists and,
assuming it does, on the ease of exploiting it and the extent of
control or compromise it would provide. The prioritized list is
used to direct a penetration test or attack against the system.
[NCS04] (See: fault tree, flaw.)
$ flooding
1. (I) An attack that attempts to cause a failure in a system by
providing more input than the system can process properly. (See:
denial of service, fairness. Compare: jamming.)
Tutorial: Flooding uses "overload" as a type of "obstruction"
intended to cause "disruption".
2. (I) The process of delivering data or control messages to every
node of a network. (RFC 3753)
$ flow analysis
(I) An analysis performed on a nonprocedural, formal, system
specification that locates potential flows of information between
system variables. By assigning security levels to the variables,
the analysis can find some types of covert channels. [Huff]
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$ flow control
1. (I) /data security/ A procedure or technique to ensure that
information transfers within a system are not made from one
security level to another security level, and especially not from
a higher level to a lower level. [Denns] (See: covert channel,
confinement property, information flow policy, simple security
property.)
2. (O) /data security/ "A concept requiring that information
transfers within a system be controlled so that information in
certain types of objects cannot, via any channel within the
system, flow to certain other types of objects." [NCSSG]
$ For Official Use Only (FOUO)
(O) /U.S. DoD/ A U.S. Government designation for information that
has not been given a security classification pursuant to the
criteria of an Executive Order dealing with national security, but
which may be withheld from the public because disclosure would
cause a foreseeable harm to an interest protected by one of the
exemptions stated in the Freedom of Information Act (Section 552
of title 5, United States Code). (See: security label, security
marking. Compare: classified.)
$ formal
(I) Expressed in a restricted syntax language with defined
semantics based on well-established mathematical concepts. [CCIB]
(Compare: informal, semiformal.)
$ formal access approval
(O) /U.S. Government/ Documented approval by a data owner to allow
access to a particular category of information in a system. (See:
category.)
$ Formal Development Methodology
(O) See: Ina Jo.
$ formal model
(I) A security model that is formal. Example: Bell-LaPadula model.
[Land] (See: formal, security model.)
$ formal proof
(I) "A complete and convincing mathematical argument, presenting
the full logical justification for each step in the proof, for the
truth of a theorem or set of theorems." [NCSSG]
$ formal specification
(I) A precise description of the (intended) behavior of a system,
usually written in a mathematical language, sometimes for the
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purpose of supporting formal verification through a correctness
proof. [Huff] (See: Affirm, Gypsy, HDM, Ina Jo.) (See: formal.)
Tutorial: A formal specification can be written at any level of
detail but is usually a top-level specification.
$ formal top-level specification
(I) "A top-level specification that is written in a formal
mathematical language to allow theorems showing the correspondence
of the system specification to its formal requirements to be
hypothesized and formally proven." [NCS04] (See: formal
specification.)
$ formulary
(I) A technique for enabling a decision to grant or deny access to
be made dynamically at the time the access is attempted, rather
than earlier when an access control list or ticket is created.
$ FORTEZZA(trademark)
(O) A registered trademark of NSA, used for a family of
interoperable security products that implement a NIST/NSA-approved
suite of cryptographic algorithms for digital signature, hash,
encryption, and key exchange. The products include a PC card
(which contains a CAPSTONE chip), and compatible serial port
modems, server boards, and software implementations.
$ Forum of Incident Response and Security Teams (FIRST)
(N) An international consortium of CSIRTs (e.g., CIAC) that work
together to handle computer security incidents and promote
preventive activities. (See: CSIRT, security incident.)
Tutorial: FIRST was founded in 1990 and, as of July 2004, had more
than 100 members spanning the globe. Its mission includes:
- Provide members with technical information, tools, methods,
assistance, and guidance.
- Coordinate proactive liaison activities and analytical support.
- Encourage development of quality products and services.
- Improve national and international information security for
governments, private industry, academia, and the individual.
- Enhance the image and status of the CSIRT community.
$ forward secrecy
(I) See: perfect forward secrecy.
$ FOUO
(O) See: For Official Use Only.
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$ FPKI
(O) See: Federal Public-Key Infrastructure.
$ fraggle attack
(D) /slang/ A synonym for "smurf attack".
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.
Derivation: The Fraggles are a fictional race of small humanoids
(represented as hand puppets in a children's television series,
"Fraggle Rock") that live underground.
$ frequency hopping
(N) Repeated switching of frequencies during radio transmission
according to a specified algorithm. [C4009] (See: spread
spectrum.)
Tutorial: Frequency hopping is a TRANSEC technique to minimize the
potential for unauthorized interception or jamming.
$ fresh
(I) Recently generated; not replayed from some earlier interaction
of the protocol.
Usage: Describes data contained in a PDU that is received and
processed for the first time. (See: liveness, nonce, replay
attack.)
$ FTP
(I) See: File Transfer Protocol.
E <- 4. Definitions -> G