NCSC-TG-004 Glossary of Computer Security Terms (Teal Book)

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NCSC-TG-004-88Library No. S-231 238

FOREWORDThis publication, Glossary of Computer Security Terms, is issued by theNational Computer Security Center (NCSC) under the authority of and in accordancewith Department of Defense (DoD) Directive 5215.1, Computer SecurityEvaluation Center. The definitions in this glossary are intended for use by U.S.Government agencies or contractors that apply the criteria of DoD Directive5200.28-STD, DoD Trusted Computer System Evaluation Criteria, in the use oftheir computer systems.

S Recommendations for revision to this publication are encouraged and will bereviewed periodically by the NCSC. Address all proposals for revision throughappropriate channelsto:National Computer Security Center9800 Savage Road

IFort George G. Meade, MD 20755-6000Attention: Chief, Criteria and Technical Guidelines Division

FatriCK K.Giallay r.lw3r 21 October 1988DirectorNational Computer Security Center

For ol by the Superintendent of Documents, Congresignal Sales Office, U.S. Government Printing Office, Washington, DC 20402


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ACKNOWLEDGMENTSRecognition is extended to Sue Berg as primary researcher for this glossary, CarolLane as the initial editor, and to Mary Whittaker as final researcher and editor.Appreciation is extended to all who contributed and refined the definitions,particularly Devolyn Duggar and Maj. Douglas Hardie, USAF.


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PREFACE

This glossary contains material drawn primarily from official documents of theUnited States Government departments and agencies. Other terms are from privateorganizations and individuals, as indicated in the Reference section at the end ofthis document.The intent of the National Computer Security Center isfor this document tofocus on terms in the field of computer security. However, because of the overlap ofcomputer security and other security disciplines, some terms such as TEMPESTareincluded.

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TABLE OF CONTENTS

FO REW O RD ............................................................... iACKNOW LEDGM ENTS .................................................... iiPR EFA CE ................................................................COMPUTER SECURITY ACRONYMS ......................................... 1COM PUTER SECURITY TERMS .............................................. 2REFEREN CES ............................................................ 54

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GLOSSARY OF COMPUTER SECURITY ACRONYMSAIS Automated Information SystemCOMPUSEC Computer SecurityCOMSEC Communications SecurityCSTVRP Computer Security Technical Vulnerability Reporting ProgramDAA Designated Approving AuthorityDAC Discretionary Access ControlDES Data Encryption StandardDPL Degausser Products ListDTLS Descriptive Top-Level SpecificationEPL Evaluated Products ListETL Endorsed Tools ListFTLS Formal Top-Level SpecificationISSO Information System Security OfficerMAC Mandatory Access ControlNCSC National Computei Security CenterNTISSC National Telecommunications and Information SystemsSecurity CommitteeOPSEC Operations SecurityPPL Preferred Products ListSAISS Subcommittee on Automated Information Systems Security ofNTISSCSSO System Security OfficerSTS Subcommittee on Telecommunications Security of NTISSCTCB Trusted Computing BaseTCSEC DoD Trusted Computer System Evaluation Criteria


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GLOSSARY OF COMPUTER SECURITY TERMS

*-property (or star property)A Bell-La Padula security model rule allowing a subject write access to an objectonly if the security level of the object dominates the security level of the subject.Also called confinement property.

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-A-

acceptance inspectionThe final inspection to determine whether or not a facility or system meetsthe specified technical and performance standards. Note: This inspection isheld immediately after facility and software testing and is the basis forcommissioning or accepting the information system.

accessA specific type of interaction between asubject and an object that results inthe flow o information from one to the other.

access controlThe process of limiting access to the resources of a system only to authorizedprograms, processes, or other systems (in a network). Synonymous withcontrolled access and limited access.

access control mechanismHardware or software features, operating procedures, managementprocedures, and various combinations of these designed to detect andprevent unauthorized access and to permit authorized access in anautomated system.

access levelThe hierarchical portion of the security level used to identify the sensitivityof data and the clearance or authorization of users. Note: The access level,in conjunction with the nonhierarchical categories, forms the sensitivitylabel of an object. See category, security level, and sensitivity label.

access listA list of users, programs, and/or processes and the specifications of access categories towhich each isassigned.

access periodA segment of time, generally expressed on adaily or weekly basis, during which accessrights prevail.

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access portA logical or physical identifier that a computer uses to distinguish different terminalinput/output data streams.

access typeThe nature of an access right to a particular device, program, or file (e.g., read, write,execute, append, modify, delete, or create).

accountabilityThe property that enables activities on a system to be traced to individuals who maythen be held responsible for their actions.

accreditationA formal declaration by the DAA that the AIS is approved to operate in a particularsecurity mode using a perscribed set of safeguards. Accreditation is the officialmanagement authorization for operation of an AIS and is based on the certificationprocess as well as other management considerations. The accreditation statementaffixes security responsibility with the DAA and shows that due care has been taken forsecurity.

accreditation authoritySynonymous with Designated Approving Authority.

add-on securityThe retrofitting of protection mechanisms, implemented by hardware or software.

administrative securityThe management constraints and supplemental controls established to provide anacceptable level of protection for data. Synonymous with procedural security.

assuranceA measure of confidence that the security features and architecture of an AISaccurately mediate and enforce the security policy.

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attackThe act of trying to bypass security controls on a system. An attack may be active,resulting in the alteration of data; or passive, resulting in the release of data. Note:The fact that an attack ismade does not necessarily mean that it will succeed. Thedegree of success depends on the vulnerability of the system or activity and theeffectiveness of existing countermeasures.

audit trailA chronological record of system activities that issufficient to enable thereconstruction, reviewing, and examination of the sequence of environments andactivities surrounding or leading to an operation, a procedure, or an event in atransaction from its inception to final results.

authenticate(1)To verify the identity of a user, device, or other entity in a computer system, oftenas a prerequisite to allowing access to resources in a system.(2)To verify the integrity of data that have been stored, transmitted, or otherwiseexposed to possible unauthorized modification.

authenticatorThe means used to confirm the identity or to verify the eligibility of a station,originator, or individual.

authorizationThe granting of access rights to a user, program, or process.

automated data processing securitySynonymous with automated information systems security.

automated information system (AIS)An assembly of computer hardware, software and/or firmware configured to collect,create, communicate, compute, disseminate, process, store, and/or control data orinformation.

automated information system securityMeasures and controls that protect an AIS against denial of service and unauthorized(accidental or intentional) disclosure, modification, or destruction of AISs and data.AIS security includes consideration of all hardware and/or software functions,

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characteristics and/or features; operational procedures, accountability procedures, andaccess controls at the central computer facility, remote computer, and terminalfacilities; management constraints; physical structures and devices; and personnel andcommunication controls needed to provide an acceptable level of risk for the AIS andfor the data and information contained in the AIS. It includes the totality of securitysafe uards needed to provide an acceptable protection level for an AIS and for datahandled by an AIS.automated security monitoring

The use of automated procedures to ensure that security controls are notcircumvented.availabilityof data

The state when data are in the place needed by the user, at the time the user needsthem, and in the form needed by the user.

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-B-

back doorSynonymous with trap door.

backup planSynonymous with contingency plan.

Bell-La Padula modelA formal state transition model of computer security policy that describes a set ofaccess control rules. In this formal model, the entities in a computer system are dividedinto abstract sets of subjects and objects. The notion of a secure state is defined, and itis proven that each state transition preserves security by moving from secure state tosecure state, thereby inductively proving that the system is secure. A system state isdefined to be secure if the only permitted access modes of subjects to objects are inaccordance with a specific security policy.. In order to determine whether or not aspecific access mode is allowed, the clearance of a subject is compared to theclassification of the object, and a determination is made as to whether the subject isauthorized for the specific access mode. See star property (*-property) and simplesecurity property.

benign environmentA nonhostile environment that may be protected from external hostile elements byphysical, personnel, and procedural security countermeasures.

between-the-lines entryUnauthorized access obtained by tapping the temporarily inactive terminal of alegitimate user. See piggyback.

beyond AlA level of trust defined by the DoD Trusted Computer System Evaluation CriteriaTCSEC) that is beyond the state-of-the-art technology available at the time the criteriawere developed. It includes all the Al-level features plus additional ones not required ttheA1 level.

browsingThe act of searching through storage to locate or acquire information withoutnecessarily knowing of the existence or the format of the information being sought.

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-C-

call backA procedure for identifying a remote terminal. In a call back, the host systemdisconnects the caller and then dials the authorized telephone number of the remoteterminal to reestablish the connection. Synonymous with dial back.

capabilityA protected identifier that both identifies the object and specifies the access rights tobe allowed to the accessor who possesses the capability. In a capability-based system,access to protected objects such as files isgranted if the would-be accessor possesses acapability for the object.

categoryA restrictive label that has been applied to classified or unclassified data as a means ofincreasing the protection of the data and further restricting access to the data.

certificationThe comprehensive evaluation of the technical and nontechnical security features ofan AIS and other safeguards, made in support of the accreditation process, thatestablishes the extent to which a particular design and implementation meet aspecified set of security requirements.

closed security environmentAn environment in which both of the following conditions hold true:(1)Application developers (including maintainers) have sufficient clearances andauthorizations to provide an acceptable presumption that they have not introducedmalicious logic. (2)Configuration control provides sufficient assurance thatapplications and the equipment are protected against the introduction of maliciouslogic prior to and during the operation of system applications.

communications security (COMSEC)Measures taken to deny unauthorized persons information derived fromtelecommunications of the U S Government concerning national security, and toensure the authenticity of such telecommunicatons. Communications security includescryptosecurity, transmission security, emission security, and physical security ofcommunications security material and information.

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compartmentA class of information that has need-to-know access controls beyond those normallyprovided for access to Confidential, Secret or Top Secret information.

compartmented security modeSee modes of operation.

compromiseA violation of the security policy of a system such that unauthorized disclosure ofsensitive information may have occurred.

compromising emanationsUnintentional data-related or intelligence-bearing signals that, if intercepted andanalyzed, disclose the information transmission received, handled, or otherwiseprocessed by any information processing equipment. See TEMPEST.

computer abuseThe misuse, alteration, disruption or destruction of data processing resources. The keyaspect is hat it is ntentional and improper.

computer cryptographyThe use of acrypto-algorithm in a computer, microprocessor, or microcomputer toperform encryption or decryption in order to protect information or to authenticateusers, sources, or information.

computer fraudComputer-related crimes involving deliberate misrepresentation, alteration ordisclosure of data in order to obtain something of value (usually for monetary gain). Acomputer system must have been involved in the perpetration or coverup of the act orseries of acts. A computer system might have been involved through impropermanipulation of input data; output or results; applications programs; data files;computer operations; communications; or computer hardware, systems software, orfirmware.

computer security (COMPUSEC)Synonymous with automated information systems security.

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computer security subsystemA device designed to provide limited computer security features in a larger systemenvironment.

Computer Security Technical Vulnerability Reporting Program (CSTVRP)A program that focuses on technical vulnerabilities in commercially availablehardware, firmware and software products acquired by DoD. CSTVRP provides for thereporting, cataloging, and discreet dissemination of technical vulnerability andcorrective measure information to DoD components on a need-to-know basis.

concealment systemA method of achieving confidentiality in which sensitive information is hidden byembedding it in irrelevant data.

confidentialityThe concept of holding sensitive data in confidence, limited to an appropriate set ofindividuals or organizations.

configuration controlThe process of controlling modifications to the system's hardware, firmware, software,and documentation that providessufficient assurance that the system is protectedagainst the introduction of improper modifications prior to, during, and after systemimplementation. Compare configuration management

configuration managementThe management of security features and assurances through control of changes madeto a system's hardware, software, firmware, documentation, test, test fixtures and testdocumentation throughout the development and operational life of the system.Compare configuration control.

confinementThe prevention of the leaking of sensitive data from a program.

confinement channelSynonymous with covert channel.

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confinement propertySynonymous with star property (*-property).

contaminationThe intermixing of data at different sensitivity and need-to-know levels. The lowerlevel data issaid to be contaminated by the higher level data; thus, the contaminating(higher level) data may not receive the required level of protection.

contingency planA plan for emergency response, backup operations, and post-disaster recoverymaintained by an activity as a part of its security program that will ensure theavailability of critical resources and facilitate the continuity of operations in anemergency situation. Synonymous with disaster plan and emergency plan.

control zoneThe space, expressed in feet of radius, surrounding equipment processing sensitiveinformation, that isunder sufficient physical and technical control to preclude anunauthorized entry or compromise.

controlled accessSee access control.

controlled sharingThe condition that exists when access control is applied to all users and components ofa system.cost-risk analysis

The assessment of the costs of providing data protection for a system versus the cost oflosing or compromising the data.countermeasure

Any action, device, procedure, technique, or other measure that reduces thevulnerability of or threat to a system.

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covert channelA communications channel that allows two cooperating processes to transferinformation in a manner that violates the system's security policy. Synonymous withconfinement channel.

covert storage channelAcovert channel that involves the direct or indirect writing of astorage location byone process and the direct or indirect reading of the storage location by anotherprocess. Covert storage channels typically involve a finite resource (e.g., sectors on adisk) that is hared by two subjects at different security levels.

covert timing channelAcovert channel in which one process signals information to another by modulatingits own use of system resources (e.g., CPU time) in such away that this manipulationaffects the real response time observed by the second process.

CriteriaSee DoD Trusted Computer System Evaluation Criteria.

crypto-algorithmA well-defined procedure or sequence of rules or steps used to produce a key streamor cipher text from plain text and vice versa.

cryptographyThe principles, means and methods for rendering information unintelligible, and forrestoring encrypted information to intelligible form.

cryptosecurityThe security or protection resulting from the proper use of technically soundcryptosystems.

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-D-

Data Encryption Standard (DES)A cryptographic algorithm for the protection of unclassified data, published in FederalInformation Processing Standard FIPS) 46. The DES, which was approved by theNational Institute of Standards and Technology, is intended for public and governmentuse.

data flow controlSynonymous with information flow control.

data integrityThe property that data meet an a priori expectation of quality.

data securityThe protection of data from unauthorized (accidental or intentional) modification,destruction, or disclosure.

declassification of AIS storage mediaAn administrative decision or procedure to remove or reduce the security classificationof the subject media.

dedicated security modeSee modes of operation.

default classificationA temporary classification reflecting the highest classification being processed in asystem. The default classification is included in the caution statement affixed to theobject.

degaussTo reduce magnetic flux density to zero by applying a reverse magnetizing field.

degausserAn electrical device that can generate a magnetic field for the purpose of degaussingmagnetic storage media.

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Degausser Products List (DPI)A list of commercially produced degaussers that meet National Security Agencyspecifications. This list is included in the NSA Information Systems Security Productsand Services Catalogue, and is available through the Government Printing Office.

denial of serviceAny action or series of actions that prevent any part of a system from functioning inaccordance with its intended purpose. This includes any action that causesunauthorized destruction, modification, or delay of service. Synonymous withinterdiction.Descriptive Top-Level Specification (DTLS)

A top-level specification that is written in a natural language (e.g., English), aninformal design notation, or a combination of the two.Designated Approving Authority (DAA)

The official who has the authority to decide on accepting the security safeguardsprescribed for an AIS or that official who may be responsible for issuing anaccreditation statement that records the decision to accept those safeguards.dial back

Synonymous with call back.dial-up

The service whereby a computer terminal can use the telephone to initiate and effectcommunication with a computer.disaster plan

Synonymous with contingency plan.

discretionary access control (DAC)A means of restricting access to objects based on the identity and need-to-know of theuser, process and/or groups to which they belong. The controls are discretionary in thesense that a subject with a certain access permission is capable of passing thatpermission (perhaps indirectly) on to any other subject. Compare mandatory accesscontrol.

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O Trusted Computer System Evaluation Criteria (TCSEC)A document published by the National Computer Security Center containing a uniformset of basic requirements and evaluation classes for assessing degrees of assurance inthe effectiveness of hardware and software security controls built into systems. Thesecriteria are intended for use in the design and evaluation of systems that will processand/or store sensitive or classified data. This document is Government Standard DoD5200.28-STD and is frequently referred to as The Criteria or The Orange Book.

domainThe unique context (e.g., access control parameters) in which a program is operating;in effect, the set of objects that a subject has the ability to access. See process andsubject.

dominateSecurity level S1 is said to dominate security level S2 if the hierarchical classification of$1 is greater than or equal to that of S2 and the nonhierarchical categories of S1 includeall those of S2 as a subset.

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-E-

emanationsSee compromising emanations.

embedded systemA system that performs or controls a function, either in whole or in part, as an integralelement of a larger system or subsystem.

emergency planSynonymous with contingency plan.

emission securityThe protection resulting from all measures taken to deny unauthorized personsinformation of value that might be derived from intercept and from an analysis ofcompromising emanations from systems.

end-to-end encryptionThe protection of information passed in a telecommunications system bycryptographic means, from point of origin to point of destination.

Endorsed Tools List ETL)The list of formal verification tools endorsed by the NCSC for the development ofsystems with high levels of trust.

Enhanced Hierarchical Development MethodologyAn integrated set of tools designed to aid in creating, analyzing, modifying,managing, and documenting program specifications and proofs. This methologyincludes aspecification parser and typech ecker, a heorem prover, and amulti-levelsecurity checker. Note: This methodology isnot based upon the HierarchicalDevelopment Methodology.

entrapmentThe deliberate planting of apparent flaws in asystem for the purpose of detectingattempted penetrations.

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environmentThe aggregate of external procedures, conditions, and objects that affect thedevelopment, operation, and maintenance of asystem.

erasureAprocess by which asignal recorded on magnetic media isremoved. Erasure isaccomplished in two ways: (1)by alternating current erasure, by which theinformation isdestroyed by applying an alternating high and low magnetic field to themedia; or (2)by direct current erasure, by which the media are saturated by applying aunidirectional magnetic field.

Evaluated Products List EPL)A ist of equipments, hardware, software, and/or firmware that have been evaluatedagainst, and found to be technically compliant, at a particular level of trust, with theDoD TCSEC by the NCSC. The EPL is ncluded in the National Security AgencyInformationSystems Security Products and Services Catalogue, which isavailablethrough the Government Printing Office.

executive stateOne of several states in which asystem may operate and the only one in which certainprivileged instructions may be executed. Such instructions cannot be executed whenthe system isoperating in other (e.g., user) states. Synonymous with supervisor state.

exploitable channelAny information channel that isusable or detectable by subjects external to thetrusted computing base whose purpose is o violate the security policy of the system.See covert channel.

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-F-fail safe

Pertaining to the automatic protection of programs and/or processing systems tomaintain safety when a hardware or software failure isdetected in a system.fail soft

Pertaining to the selective termination of affected nonessential processing when ahardware or software failure isdetected in a system.failure access

An unauthorized and usually inadvertent access to data resulting from a hardware orsoftware failure in the system.failure control

The methodology used to detect and provide fail-safe or fail-soft recovery fromhardware and software failures in a system.fault

A condition that causes a device or system component to fail to perform in a requiredmanner.fetch protection

A system-provided restriction to prevent a program from accessing data in anotheruser's segment of storage.file protection

The aggregate of all processes and procedures in a system designed to inhibitunauthorized access, contamination, or elimination of a file.file security

The means by which access to computer files is imited to authorized users only.

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flaw hypothesis methodologyA systems analysis and penetration technique in which specifications anddocumentation for the system are analyzed and then flaws in the system arehypothesized. The list of hypothesized flaws is hen prioritized on the basis of theestimated probability that a flaw exists and, assuming a flaw does exist, on the ease ofexploiting it, and on the extent of control or compromise it would provide. Theprioritized list isused to direct a penetration attack against the system.

flow controlSee information flow control.

formal access approvalDocumented approval by a data owner to allow access to aparticular category ofinformation.

Formal Development MethodologyA collection of languages and tools that enforces a rigorous method of verification.This methodology uses the Ina Jo specification language for successive stages of systemdevelopment, including identification and modeling of requirements, high-leveldesign, and program design.

formal proofA complete and convincing mathematical argument, presenting the full logicaljustification for each proof step, for the truth of a theorem or set of theorems.

formal security policy modelA mathematically precise statement of a security policy. To be adequately precise, sucha model must represent the initial state of a system, the way in which the systemprogresses from one state to another, and adefinition of a secure state of thesystem. To be acceptable as abasis for a TCB, the model must be supported by a formalproof that if the initial state of the system satisfies the definition of a secure stateand if all assumptions required by the model hold, then all future states of the systemwill be secure. Some formal modeling techniques include: state transition models,denotational semantics models, and algebraic specification models. See Bell-La Padulamodel and security policy model.

Formal Top-Level Specification FTLS)A top-level specification that iswritten in a formal mathematical language to allowtheorems showing the correspondence of the system specification to its formalrequirements to be hypothesized and formally proven.

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formal verificationThe process of using formal proofs to demonstrate the consistency between a ormalspecification of asystem and a ormal security policy model (design verification) orbetween the formal specification and its high level program implementation(implementation verification).

front-end security filterA security filter, which could be implemented in hardware or software, that is ogicallyseparated from the remainder of the system to protect the system's integrity.

functional testingThe segment of security testing in which the advertised security mechanisms of thesystem are tested, under operational conditions, for correct operation.

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-G-

granularityAn expression of the relative size of a data object; e.g., protection at the file level isconsidered coarse granularity, whereas protection at field level is considered to be of afiner granularity.

guardA processor that provides a filter between two disparate systems operating at differentsecurity levels or between a user terminal and a data base to filter out data that theuser isnot authorized to access.

Gypsy Verification EnvironmentAn integrated set of tools for specifying, coding, and verifying programs written in theGypsy language, a language similar to Pascal which has both specification andprogramming features. This methology includes an editor, aspecification processor, averification condition generator, a user-directed theorem prover, and an informationflow tool.

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-H-handshaking procedure

A dialogue between two entities (e.g., a user and a computer, a computer and anothercomputer, or a program and another program) for the purpose of identifying andauthenticating the entities to one another.Hierarchical Development Methodology

A methodology for specifying and verifying the design programs written in the Specialspecification language. The tools for this methodology include the Specialspecification processor, the Boyer-Moore theorem prover, and the Feiertaginformation flow tool.host to front-end protocol

A set of conventions governing the format and control of data that are passed from ahost to a front-end machine.

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-I-

identificationThe process that enables recognition of an entity by a system, generally by the use ofunique machine-readable user names.

impersonatingSynonymous with spoofing.

incomplete parameter checkingA system design flaw that results when all parameters have not been fully anticipatedfor accuracy and consistency, thus making the system vulnerable to penetration.

individual accountabilityThe ability to associate positively the identity of auser with the time, method, anddegree of access to a system.

information flow controlA procedure to ensure that information transfers within a system are not made from ahigher security level object to an object of a lower security level. See covert channel,simple security property, star property (--property). Synonymous with data flowcontrol and flow control.

Information System Security Officer (ISSO)The person responsible to the DAA for ensuring that security is provided for andimplemented throughout the life cycle of an AIS from the beginning of the conceptdevelopment plan through its design, development, operation, maintenance, andsecure disposal.

Information Systems SecurityProductsand Services CatalogueA catalogue issued quarterly by the National Security Agency that incorporates theDPL, EPL, ETL, PPL and other security product and service lists. This catalogue isavailable through the U.S. Government Printing Office, Washington, DC 20402,(202) 783-3238.

integritySound, unimpaired or perfect condition.

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interdictionSee denial of service.

internal security controlsHardware, firmware, and software features within a system that restrict access toresources (hardware, software, and data) to authorized subjects only (persons,programs, or devices).

isolationThe containment of subjects and objects in a system in such a way that they areseparated from one another, as well as from the protection controls of the operatingsystem.

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.J.

This document contains no entries beginning with the letter J .

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-K-

This document contains no entries beginning with the letter K .

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-1-

least privilegeThe principle that requires that each subject be granted the most restrictive set ofprivileges needed for the performance of authorized tasks. The application of thisprinciple limits the damage that can result from accident, error, or unauthorized use.

limited accessSynonymous with access control.

list-orientedA computer protection system in which each protected object has a list of all subjectsauthorized to access it. Compare ticket-oriented.

lock-and-key protection systemA protection system that involves matching a key or password with a specific accessrequirement.

logic bombA resident computer program that triggers the perpetration of an unauthorized actwhen particular states ofthe system are realized.

loopholeAn error of omission or oversight in software or hardware that permits circumventingthe system security policy.

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I-

magnetic remanenceA measure of the magnetic flux density remaining after removal of the appliedmagnetic force. Refers to any data remaining on magnetic storage media afterremoval of the power.

maintenance hookSpecial instructions in software to allow easy maintenance and additional featuredevelopment. These are not clearly defined during access for design specification.Hooks frequently allow entry into the code at unusual points or without the usualchecks, so they are a serious security risk if they are not removed prior to liveimplementation. Maintenance hooks are special types of trap doors.

malicious logicHardware, software, or firmware that is intentionally included in a system for anunauthorized purpose; e.g., aTrojan horse.

mandatory access control (MAC)A means of restricting access to objects based on the sensitivity (as represented by alabel) of the information contained in the objects and the formal authorization (i.e.,clearance) of subjects to access information of such sensitivity. Compare discretionaryaccess control.

masqueradingSynonymous with spoofing.

mimickingSynonymous with spoofing.

modes of operationA description of the conditions under which an AIS functions, based on the sensitivityof data processed and the clearance levels and authorizations of the users. Four modesof operation are authorized:

(1) Dedicated ModeAn AIS isoperating in the dedicated mode when each user with direct or indirectindividual access to the AIS, its peripherals, remote terminals, or remote hosts, hasall of the following:

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a.A valid personnel clearance for all information on the system.b. Formal access approval for, and has signed nondisclosure agreements for allthe information stored and/or processed (including all compartments,subcompartments and/or special access programs).c.A valid need-to-know for all information contained within the system.(2) System-High ModeAn AIS is operating in the system-high mode when each user with direct or indirectaccess to the AIS, its peripherals, remote terminals, or remote hosts has all of thefollowing:a.A valid personnel clearance for all information on the AIS.b.Formal access approval for, and has signed nondisclosure agreements for allthe information stored and/or processed (including all compartments,subcompartments, and/or special access programs).c.A valid need-to-know for some of the information contained within the AIS.(3) Compartmented ModeAn AIS isoperating in the compartmented mode when each user with direct orindirect access to the AIS, its peripherals, remote terminals, or remote hosts, has allof the following:

a. A valid personnel clearance for the most restricted information processedin the AIS.b.Formal access approval for, and has signed nondisclosure agreements forthat information to which he/she isto have access.c. A valid need-to-know for that information to which he/she isto have access.(4) Multilevel ModeAn AIS isoperating in the multilevel mode when all the following statements aresatisfied concerning the users with direct or indirect access to the AIS, itsperipherals, remote terminals, or remote hosts:a. Some do not have a valid personnel clearance for all the informationrocessed in the AIS..All have the proper clearance and have the appropriate formal accessapproval for that information to which he/she isto have access.c.All have avalid need-to-know for that information to which they are tohave access.

multilevel deviceA device that isused in a manner that permits it to simultaneously process data of twoor more security levels without risk of compromise. To accomplish this, sensitivitylabels are normally stored on the same physical medium and in the same form (i.e.,machine-readable or human-readable) as the data being processed.

multilevel secureA class of system containing information with different sensitivities thatsimultaneously permits access by users with different security clearances and needs-to-know, but prevents users from obtaining access to information for which they lackauthorization.

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multilevel security modeSee modes of operation.

multiple access rights terminalA terminal that may be used by more than one class of users; for example, users withdifferent access rights to data.

multiuser mode of operationA mode of operation designed for systems that process sensitive unclassifiedinformation in which users may not have a need-to-know for all information processedin the system. This mode isalso for microcomputers processing sensitive unclassifiedinformation that cannot meet the requirements of the stand-alone mode of operation.

mutually suspiciousThe state that exists between interacting processes (subsystems or programs) in whichneither process can expect the other process to function securely with respect to someproperty.

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-N-

National Computer Security Assessment ProgramA program designed to evaluate the interrelationship of empirical data of computersecurity infractions and critical systems profiles, while comprehensively incorporatinginformation from the CSTVRP. The assessment will build threat and vulnerabilityscenarios that are based on a collection of facts from relevant reported cases. Suchscenarios are a powerful, dramatic, and concise form of representing the value of lossexperience analysis.

National Computer Security Center (NCSC)Originally named the DoD Computer Security Center, the NCSC is responsible forencouraging the widespread availability of trusted computer systems throughout theFederal Government.

National Security Decision Directive 145 (NSDD 145)Signed by President Reagan on 17 September 1984, this directive is entitled NationalPolicy on Telecommunications and Automated Information Systems Security. Itprovides initial objectives, policies, and an organizational structure to guide theconduct of national activities toward safeguarding systems that process, store, orcommunicate sensitive information; establishes a mechanism for policy development;and assigns implementation responsibilities.

National Telecommunications and Information Systems Security Advisory Memoranda/Instructions (NTISSAM, NTISSI)NTISS Advisory Memoranda and Instructions provide advice, assistance, or informationof general interest on telecommunications and systems security to all applicablefederal departments and agencies. NTISSAMs/NTISSIs are promulgated by the NationalManager for Telecommunications and Automated Information Systems Security andare recommendatory.

National Telecommunications and Information System Security Directives (NTISSD)NTISS Directives establish national-level decisions relating to NTISS policies, plans,programs, systems, or organizational delegations of authority. NTISSDs arepromulgated by the Executive Agent of the Government for Telecommunications andInformation Systems Security, orby the Chairman of the NTISSC when so delegated bythe Executive Agent. NTISSDs are binding upon all federal departments and agencies.

need-to-knowThe necessity for access to, knowledge of, or possession of specific informationrequired to carry out official duties.

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network front endA device that implements the necessary network protocols, including security-relatedprotocols, to allow a computer system to be attached to a network.

NSDD 145See National Security Decision Directive 145.

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-0-

objectA passive entity that contains or receives information. Access to an object potentiallyimplies access to the information it contains. Examples of objects are: records, blocks,pages, segments, files, directories, directory trees, and programs, as well as bits, bytes,words, fields, processors, video displays, keyboards, clocks, printers, and networknodes.

object reuseThe reassignment and reuse of a storage medium (e.g., page frame, disk sector,magnetic tape) that once contained one or more objects. To be securely reused andassigned to a new subject, storage media must contain no residual data (magneticremanence) from the object(s) previously contained in the media.

open security environmentAn environment that includes those systems in which at least one of the followingconditions holds true: (I) Application developers (including maintainers) do nothavesufficient clearance or authorization to provide an acceptable presumption that theyhave not introduced malicious logic. (2) Configuration control does not providesufficient assurance that applications are protected against the introduction ofmalicious logic prior to and during the operation of system applications.

Operations Security (OPSEC)An analytical process by which the U.S. Government and its supporting contractors candeny to potential adversaries information about capabilities and intentions byidentifying, controlling, and protecting evidence of the planning and execution ofsensitive activities and operations.

Orange BookAlternate name for DoD Trusted Computer Security Evaluation Criteria.

overt channelA path within a computer system or network that is designed for the authorizedtransfer of data. Compare covert channel.

overwrite procedureA stimulation to change the state of a bit followed by a known pattern. See magneticremanence.

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.P

partitioned security modeA mode of operation wherein all personnel have the clearance but not necessarilyformal access approval and need-to-know for all information contained in the system.Not to be confused with compartmented security mode.

passwordA protected/private character string used to authenticate an identity.

penetrationThe successful act of bypassing the security mechanisms of a system.

penetration signatureThe characteristics or identifying marks that may be produced by a penetration.

penetration studyA study to determine the feasibility and methods for defeating controls of a system.

penetration testingThe portion of security testing in which the evaluators attempt to circumvent thesecurity features of a system. The evaluators may be assumed to use all system designand implementation documentation, which may include listings of system source code,manuals, and circuit diagrams. The evaluators work under the same constraintsapplied to ordinary users.

periods processingThe processing of various levels of sensitive information at distinctly different times.Under periods processing, the system must be purged of all information from oneprocessing period before transitioning to the next when there are different users withdiffering authorizations.

permissionsA description of the type of authorized interactions a subject can have with an object.Examples include: read, write, execute, add, modify, and delete.

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personnel securityThe procedures established to ensure that all personnel who have access to sensitiveinformation have the required authority as well as appropriate clearances.

physical securityThe application of physical barriers and control procedures as preventive measures orcountermeasures against threats to resources and sensitive information.

piggybackGaining unauthorized access to a system via another user's legitimate connection. Seebetween-the-lines entry.

Preferred Products List PPL)A list of commercially produced equipments that meet TEMPEST and otherrequirements prescribed by the National Security Agency. This list is included in theNSA Information Systems Security Products and Services Catalogue, issued quarterlyand available through the Government Printing Office.

print suppressionEliminating the displaying of characters in order to preserve their secrecy; e.g., notdisplaying the characters of a password as it iskeyed at the input terminal.

privileged instructionsA set of instructions (e.g., interrupt handling or special computer instructions) tocontrol features (such as storage protection features) that are generally executableonly when the automated system is operating in the executive state.procedural security

Synonymous with administrative security.process

A program in execution. See domain and subject.protection philosophy

An informal description of the overall design of a system that delineates each of theprotection mechanisms employed. A combination, appropriate to the evaluation class,

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of formal and informal techniques isused to show that the mechanisms are adequateto enforce the security policy.protection ring

One of a hierarchy of privileged modes of a system that gives certain access rights touser programs and processes authorized to operate in a given mode.protection-critical portions of the TCB

Those portions of the TCB whose normal function isto deal with the control of accessbetween subjects and objects. Their correct operation isessential to the protection ofthe data on the system.protocols

A set of rules and formats, semantic and syntactic, that permits entities to exchangeinformation.pseudo-flaw

An apparent loophole deliberately implanted in an operating system program as atrap for intruders.Public Law 100-235 (P.L. 100-235)

Also known as the Computer Security Act of 1987, this law creates a means forestablishing minimum acceptable security practices for improving the security andprivacy of sensitive information in federal computer systems. This law assigns to theNational Institute of Standards and Technology responsibility for developingstandards and guidelines for federal computer systems processing unclassified data.The law also requires establishment of security plans by all operators of federalcomputer systems that contain sensitive information.

purgeThe removal of sensitive data from an AIS, AIS storage device, or peripheral devicewith storage capacity, at the end of a processing period. This action isperformed insuch a way that there isassurance proportional to the sensitivity of the data that thedata may not be reconstructed. An AIS must be disconnected from any externalnetwork before a purge. After a purge, the medium can be declassified by observingthe review procedures of the respective agency.

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This document contains no entries beginning with the letter Q .

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-R-

readA fundamental operation that results only in the flow of information from an object toa subject.

read accessPermission to read information.

recovery proceduresThe actions necessary to restore a system's computational capability and data filesafter a system failure.

reference monitor conceptAn access-control concept that refers to an abstract machine that mediates all accessesto objects by subjects.reference validation mechanism

An implementation of the reference monitor concept. A security kernel isa type ofreference validation mechanism.reliability

The probability of a given system performing its mission adequately for a specifiedperiod of time under the expected operating conditions.residual risk

The portion of risk that remains after security measures have been applied.residue

Data left in storage after processing operations are complete, but before degaussingor rewriting has taken place.resource encapsulation

The process of ensuring that a resource not be directly accessible by a subject, but thatit be protected so that the reference monitor can properly mediate accesses to it.

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restricted areaAny area to which access issubject to special restrictions or controls for reasons ofsecurity or safeguarding of property or material.

riskThe probability that a particular threat will exploit a particular vulnerability of thesystem.

risk analysisThe process of identifying security risks, determining their magnitude, and identifyingareas needing safeguards. Risk analysis isa part of risk management. Synonymouswith risk assessment.

risk assessmentSynonymous with risk analysis.

risk indexThe disparity between the minimum clearance or authorization of system users andthe maximum sensitivity (e.g., classification and categories) of data processed by asystem. See CSC-STD-003-85 and CSC-STD-004-85 for acomplete explanation of thisterm.

risk managementThe total process of identifying, controlling, and eliminating or minimizin uncertainevents that may affect system resources. It includes risk anaysis, cost beneit analysis,selection, implementation and test, security evaluation of safeguards, and overallsecurity review.

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-S-

safeguardsSee security safeguards.

scavengingSearching through object residue to acquire unauthorized data.

secure configuration managementThe set of procedures appropriate for controlling changes to asystem's hardware andsoftware structure for the purpose of ensuring that changes will not lead to violationsof the system's security policy.

secure stateAcondition in which no subject can access any object in an unauthorized manner.secure subsystem

Asubsystem that contains its own implementation of the reference monitor conceptfor those resources it controls. However, the secure subsystem must depend on othercontrols and the base operating system for the control of subjects and the moreprimitive system objects.security critical mechanisms

Those security mechanisms whose correct operation isnecessary to ensure that thesecurity policy isenforced.security evaluation

An evaluation done to assess the degree of trust that can be placed in systems for thesecure handling of sensitive information. One type, aproduct evaluation, isanevaluation performed on the hardware and software features and assurances of acomputer product from a perspective that excludes the application environment. Theother type, asystem evaluation, isdone for the purpose of assessing asystem's securitysafeguards with respect to aspecific operational mission and isa major step in thecertification and accreditation process.security fault analysis

A security analysis, usually performed on hardware at gate level, to determine thesecurity properties of adevice when ahardware fault isencountered.

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security featuresThe security-relevant functions, mechanisms, and characteristics of system hardwareand software. Security features are a subset of system security safeguards.

security filterA trusted subsystem that enforces a security policy on the data that pass through it.

security flawAn error of commission or omission in a system that may allow protection mechanismsto be bypassed.

security flow analysisA security analysis performed on a formal system specification that locates potentialflows of information within the system.

security kernelThe hardware, firmware, and software elements of a TCB that implement thereference monitor concept. It must mediate all accesses, be protected frommodification, and be.verifiable as correct.

security labelA piece of information that represents the security level of an object.

security levelThe combination of a hierarchical classification and a set of nonhierarchical categoriesthat represents the sensitivity of information.

security measuresElements of software, firmware, hardware, or procedures that are included in a systemfor the satisfaction of security specifications.

security perimeterThe boundary where security controls are in effect to protect assets.

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security policyThe set of laws, rules, and practices that regulate how an organization manages,protects, and distributes sensitive information.

security policy modelA formal presentation of the security policy enforced by the system. It must identifythe set of rules and practices that regulate how a system manages, protects, anddistributes sensitive information. See Bell-La Padula model and formal security policymodel.

security rangeThe highest and lowest security levels that are permitted in or on a system, systemcomponent, subsystem or network.

security requirementsThe types and levels of protection necessary for equipment, data, information,applications, and facilities to meet security policy.

security requirements baselineUA description of minimum requirements necessary for a system to maintain anacceptable level of security.

security safeguardsThe protective measures and controls that are prescribed to meet the securityrequirements specified for a system. Those safeguards may include but are notnecessarily limited to: hardware and software security features, operating procedures,accountability procedures,access and distribution controls, management constraints,personnel security, and physical structures, areas, and devices. Also called safeguards.

security specificationsA detailed description of the safeguards required to protect a system.

security test and evaluationAn examination and analysis of the security safeguards of a system as they have beenapplied in an operational environment to determine the security posture of thesystem.

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security testingA process used to determine that the security features of a system are implemented aslesi?ned. This includes hands-on functional testing, penetration testing, andverification.

sensitive informationAny information, the loss, misuse, modification of, or unauthorized access to, couldaffect the national interest or the conduct of Federal programs, or the privacy to whichindividuals are entitled under Section 552a of Title 5, U.S. Code, but that has not beenspecifically authorized under criteria established by an Executive order or an act ofCongress to be kept classified in the interest of national defense or foreign policy.sensitivity label

A piece of information that represents the security level of an object. Sensitivity labelsare used by the TCB as the basis for mandatory access control decisions.simple security condition

See simple security property.simple security property

A Bell-La Padula security model rule allowing a subject read access to an object only ifthe security level of the subject dominates the security level of the object. Synonymouswith simple security condition.single-level device

An automated information systems device that isused to process data of asinglesecurity level at any one time.Software Development Methodologies

Methodologies for specifying and verifying design programs for system development.Each methodology iswritten for aspecific computer language. See EnhancedHierarchical Development Methodology, Formal Development Methodology, GypsyVerification Environment and Hierarchical Development Methodology.

software securityGeneral purpose (executive, utility or software development tools) and applicationsprograms or routines that protect data handled by a system.

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software system test and evaluation processA process that plans, develops and documents the quantitative demonstration of thefulfillment of all baseline functional performance, operational and interfacerequirements.

spoofingAn attempt to*gain access to a system by posing as an authorized user. Synonymouswith impersonating, masquerading or.mimicking.

stand-alone, shared systemA system that isphysically and electrically isolated from all other systems, and isintended to be used by more than one person, either simultaneously (e.g., a systemwith multiple terminals) or serially, with data belonging to one user remainingavailable to the system while another user isusing the system (e.g., a personalcomputer with nonremovable storage media such as a hard disk).

stand-alone, single-user systemA system that isphysically and electrically isolated from all other systems, and isintended to be used by one person at a time, with no data belonging to other usersremaining in the system (e.g., a personal computer with removable storage media suchas a floppy disk).

star propertySee -property, page 2.

State Delta Verification SystemA system designed to give high confidence regarding microcode performance by usingformulae that represent isolated states of acomputation to check proofs concerningthe course of that computation.

state variableA variable that represents either the state of the system or the state of some systemreso u rce.

storage objectAn object that supports both read and write accesses.

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Subcommittee on Automated Information Systems Security (SAISS)NSDD-145 authorizes and directs the establishment, under the NTISSC, of a permanentSubcommittee on Automated Information Systems Security. The SAISS iscomposed ofone voting member from each organization represented on the NTISSC.

Subcommittee on Telecommunications Security STS)NSDD-145 authorizes and directs the establishment, under the NTISSC, of a permanentSubcommittee on Telecommunications Security. The STS iscomposed of one votingmember from each organization represented on the NTISSC.

subjectAn active entity, generally in the form of a person, process, or device, that causesinformation to flow among objects or changes the system state. Technically, aprocess/domain pair.

subject security levelA subject's security level isequal to the security level of the objects to which it has bothread and write access. A subject's security level must always be dominated by theclearance of the user with which the subject isassociated.

supervisor stateSynonymous with executive state.

System Development MethodologiesMethodologies developed through software engineering to manage the complexityof system development. Development methodologies include software engineeringaids and high-level design analysis tools.

system high security modeSee modes ofoperation.

system integrityThe quality that a system has when it performs its intended function in an unimpairedmanner, free from deliberate or inadvertent unauthorized manipulation of thesystem.

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system lowThe lowest security level supported by a system at a particular time or in a particularenvironment.

System Security Officer (SSO)See Information System Security Officer.

Systems Security Steering GroupThe senior government body established by NSDD-145 to provide top-level review andpolicy guidance for the telecommunications security and automated informationsystems security activities of the U.S. Government. This group is chaired by theAssistant to the President for National Security Affairs and consists of the Secretary ofState, Secretary of Treasury, the Secretary of Defense, the Attorney General, theDirector of the Office of Management and Budget, and the Director of CentralIntelligence.

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-T-

tamperingAn unauthorized modification that alters the proper functioning of an equipment orsystem in a manner that degrades the security or functionality it provides.

technical attackAn attack that can be perpetrated by circumventing or nullifying hardware andsoftware protection mechanisms, rather than by subverting system personnel or otherusers.

technical vulnerabilityA hardware, firmware, communication, or software flaw that leaves a computerprocessing system open for potential exploitation, either externally or internally,thereby resulting in risk for the owner, user, or manager of the system.

TEMPESTThe study and control of spurious electronic signals emitted by electrical equipment.

terminal identificationThe means used to uniquely identify a terminal to a system.

threatAny circumstance or event with the potential to cause harm to a system in the form ofdestruction, disclosure, modification of data, and/or denial of service.

threat agentA method used to exploit avulnerability in a system, operation, or facility.

threat analysisThe examination of all actions and events that might adversely affect a system oroperation.

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threat monitoringThe analysis, assessment, and review of audit trails and other data collected for thepurpose of searching out system events that may constitute violations or attemptedviolations of system security.

ticket-orientedA computer protection system in which each subject maintains a ist of unforgeable bitpatterns, called tickets, one for each object the subject isauthorized to access.Compare list-oriented.

time-dependent passwordA password that isvalid only at acertain time of day or during a specified interval oftime.

top-level specificationA nonprocedural description of system behavior at the most abstract level; typically, afunctional specification that omits all implementation details.

tranquilityA security model rule stating that the security level of an object cannot change whilethe object isbeing processed by an AIS.

trap doorA hidden software or hardware mechanism that can be triggered to permit systemprotection mechanisms to be circumvented. It is activated in some innocent-appearingmanner; e.g., a special random key sequence at a terminal. Software developersoften introduce trap doors in their code to enable them to reenter the system andperform certain functions. Synonymous with back door.Trojan horse

A computer program with an apparently or actually useful function that containsadditional (hidden) functions that surreptitiously exploit the legitimate authorizationsof the invoking process to the detriment of security or integrity.trusted computer system

A system that employs sufficient hardware and software assurance measures to allowits use for simultaneous processing of a range of sensitive or classified information.

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Trusted Computing Base (TCB)The totality of protection mechanisms within a computer system, including hardware,firmware, and software, the combination of which is responsible for enforcing asecurity policy. A TCB consists of one or more components that together enforce aunified security policy over a product or system. The ability of a TCB to enforcecorrectly a unified security policy depends solely on the mechanisms within the TCBand on the correct inpUt by system administrative personnel of parameters (e.g., auser's clearance level)related to the security policy.

trusted distributionA trusted method for distributing the TCB hardware, software, and firmwarecomponents, both originals and updates, that provides methods for protecting the TCBfrom modification during distribution and for detection of any changes to the TCBthat may occur.

trusted identification forwardingAn identification method used in networks whereby the sending host can verify thatan authorized user on its system is attempting a connection to another host. Thesending host transmits the required user authentication information to the receivinghost. The receiving host can then verify that the user is validated for access to itssystem. This operation may be transparent to the user.trusted path

A mechanism by which a person at a terminal can communicate directly with the TCB.This mechanism can only be activated by the person or the TCB and cannot be imitatedby untrusted software.trusted process

A process whose incorrect or malicious execution is capable of violating system securitypolicy.trusted software

The software portion of the TCB.

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-U-untrusted process

A process that has not been evaluated or examined for adherence to the secuitypolicy. It may include incorrect or malicious code that attempts to circumvent thesecurity mechanisms.

userPerson or process accessing an AIS either by direct connections (i.e., via terminals), orindirect connections (i.e., prepare input data or receive output that is not reviewed forcontent or classification by a responsible individual).

user IDA unique symbol or character string that isused by a system to identify a specific user.

user profilePatterns of a user's activity that can be used to detect changes in normal routines.

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-V-

verificationThe process of comparing two levels of system specification for proper correspondence(e.g., security policy model with top level specification, top-level specification withsource code, or source code with object code). This process may or may not beautomated.

virusAself-propagating Trojan horse, composed of amission component, a triggercomponent, and aself-propagating component.

vulnerabilityAweakness in system security procedures, system design, implementation, internalcontrols, etc., that could be exploited to violate system security policy.

vulnerability analysisThe systematic examination of systems in order to determine the adequacy of securitymeasures, identify security deficiencies, and provide data from which to predict theeffectiveness of proposed security measures.

vulnerability assessmentA measurement of vulnerability which includes the susceptibility of a particular systemto a specific attack and the opportunities available to a threat agent to mount thatattack.

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W -

work factorAn estimate of the effort or time needed by apotential penetrator with specifiedexpertise and resources to overcome a protective measure.

writeA fundamental operation that results only in the flow of information from a subject toan object.

write accessPermission to write to an object.

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X Y ZThis document contains no entries beginning with the letters X, Y, or Z.

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REFERENCESAir Force Regulation 700-10, Information Systems Security, 15 March 1985.Army Regulation 380-380, Automated Systems Security, 3 March 1985.Department of Defense Computer Security Center, CSC-STD-002-85, Departmentof Defense Password Management Guideline, 12 April 1985.Department of Defense Computer Security Center, CSC-STD-003-85, ComputerSecurity Requirements -- Guidance for Applying the Department of Defense TrustedComputer System Evaluation Criteria to Specific Environments, 25 June 1985.Department of Defense Computer Security Center, CSC-STD-004-85, TechnicalRationale Behind CSC-STD-003-85: Computer Security Requirements -- Guidance forApplying the Department of Defense Trusted Computer System Evaluation Criteriain Specific Environments, 25 June 1985.Department of Defense Directive 5200.1-R, Information Security ProgramRegulation, June 1986.Department of Defense Directive 5200.28, Security Requirements for AutomatedInformation Systems, 21 March 1988Department of Defense Directive 5200.28-M, ADP Security Manual, January 1973.Department of Defense Directive 5200.28-STD, Department of Defense TrustedComputer System Evaluation Criteria, December 1985.Department of Defense Directive 5215.1, Computer Security Evaluation Center,25 October 1982.Department of Defense Directive 5230.25, Withholding of Unclassified TechnicalData from Public Disclosure, 6 November 1984.Department of Defense Directive 7040.6, Internal Control Systems, 24 March1982.Department of Defense Instruction 5215.2, Computer Security TechnicalVulnerability Reporting Program (CSTVRP), 2 September 1986.Department of Energy Order 5635.1A, Control of Classified Documents andInformation, 12 February 1988.Department of Energy Order 5637.1, Classified Computer Security Program,29 January 1988.Director of Central Intelligence Directive 1/16, Security Policy for UniformProtection of Intelligence Processed in Automated Information Systems andNetworks,' 19 July 1988. (SECRET)

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Mitre Corp. Technical Report MTR-8201, Trusted Computer Systems- Glossary,March 1981.National Security Decision Directive 145, National Policy on Telecommunicationsand Automated Systems Security, 17 December 1984.Office of Navy Operations Instruction 5239.1A, Department of the Navy AutomaticData Processing Security Program, 8 March 1982.Public Law 100-235, Computer Security Act of 1987, 8 January 1988.Stein, Jess (ed.), The Random House Dictionary of the English Language, RandomHouse, 1982.

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UNCLASSIFIEDSECURITY CLASSIFICATION OF THIS PAGE

REPORT DOCUMENTATION PAGEl a. REPORT SECURITY CLASSIFICATION 1b. RESTRICTIVE MARKINGSUNCLASSIFIED2a. SECURITY CLASSIFICATION AUTHORITY 3. DISTRIBUTION/AVAILABILITY OF REPORTUnlimited Distribution2b. DECLASSIFICATION/DOWNGRADING SCHEDULE

4. PERFORMING ORGANIZATION REPORT NUMBER(S) S. MONITORING ORGANIZATION REPORT NUMBER(S)NCSC-TG-004 Ubrary No.: S-231,2386a. NAME OF PERFORMING ORGANIZATION 6b. OFFICE SYMBOL 7a. NAME OF MONITORING ORGANIZATIONNational Com puter Security Centser wt, ) Cl I6c. ADDRESS (City, taf andZIP Code) 7b. ADDRESS (City, Soak andZIPCods)ATTN: C1I9800 Savage RoadFt. George G.Meade. MD 20755-6000Ba. NAME OF FUNDING/SPONSORING 8b. OFFICE SYMBOL 9. PROCUREMENT INSTRUMENT IDENTIFICATION NUMBERORGANIZATION 14PIOCONO

8c. ADDRESS (City,State andZIPCode) 10. SOURCE OF FUNDING NOS.PROGRAM PROJECT TASK WORK UNITELEMENT NO. NO. NO. NO.

11 TITLE (Include SecurityClauffcation)Glossary of Computer Security Terms12. PERSONAL AUTHOR(S)Whittaker, Mary S.; Berg, Sue13a. TYPE OF REPORT 13b. TIME COVERED 14. DATE OF REPORT (Yr, Mo., Day) 1S. PAGE COUNTFinal FROM TO 881021 5816. SUPPLEMENTARY NOTATION

17. COSATI CODES 18. SUBJECT TERMS Continueon revene If necesaryand dentfy y block number)FIELD GROUP SUB. GR. INCSC, Public LaW 100-235, NSDD 145, Trusted Computing BaseFIELD__GROUP __U_.___. (TCB), Trusted Computer System Evaluation Criteria TCSEC),Orange Book, computer security, risk analysis, vulnerabilityassessment

19. ABSTRACT (Continue on reverseside ifnecessaryand identify by block number)Glossary of Computer Security terms chiefly from National Computer Security Center and otherofficial government sources.Terms on a broad range of topics, including risk analysis, vulnerabilityassessment, and Orange Book.

20. DISTRIBUTIOW/AVAILABILITY OF ABSTRACT 2 1. ABSTRACT SECURITY CLASSIFICATIONUNCLASSIFIEDPULIMITED UNCLASSIFIED

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