Final Exam 660 Study Guide Questions
And Actual Answers.
Several security models exist, and all of them can help understand how security enters into
computer architectures and operating system design - Answer -Trusted Computing Base (TCB)
-State Machine Model
-Information Flow & Noninterference Model
-Take-Grant Model
-Access Control Matrix
-Bell-LaPadula Model
-Biba Model
-Clark-Wilson Model
-Brewer and Nash Model (aka Chinese Wall)
The foundation upon which security models are built is the - Answer Trusted Computing Base
(TCB)
An old U.S. Department of Defense standard known as the Orange Book describes a Trusted
Computing Base (TCB) as - Answer "a combination of hardware, software, and controls that
work together to form a trusted base to enforce your security policy"
The TCB is a subset of a complete information system - Answer -It should be as small as
possible so that a detailed analysis can ensure that the system meets design specifications and
requirements
-The TCB is the only portion of that system that can be trusted to enforce the security policy
In general, TCB components in a system are responsible for - Answer controlling access to the
system
-It is the responsibility of TCB components to ensure that a system behaves properly and
adheres to the security policy under all circumstances
,The part of the TCB that validates access to every resource prior to granting access requests is
called the - Answer Reference Monitor
The reference monitor may be a conceptual part of the TCB - Answer -It doesn't need to be an
actual, stand-alone system component
-The collection of components in the TCB that work together to implement reference monitor
functions is called the security kernel
The reference monitor requires - Answer descriptive information about each resource that it
protects
-Such information normally includes its classification and designation
The Bell-LaPadula and Biba models are both - Answer Information flow models
What is the difference between the Bell-LaPadula and Biba models - Answer -Bell-LaPadula is
concerned with preventing information from flowing from a high security level to a low security
level
-Biba is concerned with preventing information from flowing from a low security level to a high
security level
Techniques for Ensuring CIA? - Answer 1. Confinement
2. Bounds
3. Isolation
4. Controls
What is the Confinement technique for ensuring CIA? - Answer Process confinement allows a
process to read from and write to only certain memory locations and resources
enforced by the operating system
•If a process attempts to initiate an action beyond its granted authority, that action is denied
, •The authority level tells the OS how to set the bounds for a process (e.g. , the memory
addresses and resources it can access)
•These bounds can be either logical or physical
What is Isolation technique for ensuring CIA? - Answer -When a process is confined through
enforcing access bounds, that process runs in isolation
•Process isolation ensures that any behavior will affect only the memory and resources
associated with the isolated process
What is Control technique for ensuring CIA? - Answer -Controls use access rules to limit the
access by a subject to an object
The Biba model is also built on a state machine concept, and is characterized by two basic
properties - Answer 1. -The Simple Integrity Property states that a subject cannot read an
object at a lower integrity level (no read down)
-When integrity is important, you do not want unvalidated data read into validated documents
•The potential for data contamination is too great to permit such access
2. -The * (star) Integrity Property states that a subject cannot modify an object at a higher
integrity level (no write up)
-A subject cannot write to an object at a higher integrity level
What are Closed Systems? - Answer -Designed to work with a narrow range of other systems,
generally all from the same manufacturer
Standards for closed systems are often proprietary and not normally disclosed
What is an Open System? - Answer -Designed using agreed-upon industry standards
•Much easier to integrate with systems from different manufacturers
There is also a distinction between open-source and closed-source systems - Answer -In open-
source solutions source code and internal logic are exposed to the public
•Dependent upon public inspection / review to improve the product over time
-In closed-source (or commercial) solutions source code and internal logic are hidden from the
And Actual Answers.
Several security models exist, and all of them can help understand how security enters into
computer architectures and operating system design - Answer -Trusted Computing Base (TCB)
-State Machine Model
-Information Flow & Noninterference Model
-Take-Grant Model
-Access Control Matrix
-Bell-LaPadula Model
-Biba Model
-Clark-Wilson Model
-Brewer and Nash Model (aka Chinese Wall)
The foundation upon which security models are built is the - Answer Trusted Computing Base
(TCB)
An old U.S. Department of Defense standard known as the Orange Book describes a Trusted
Computing Base (TCB) as - Answer "a combination of hardware, software, and controls that
work together to form a trusted base to enforce your security policy"
The TCB is a subset of a complete information system - Answer -It should be as small as
possible so that a detailed analysis can ensure that the system meets design specifications and
requirements
-The TCB is the only portion of that system that can be trusted to enforce the security policy
In general, TCB components in a system are responsible for - Answer controlling access to the
system
-It is the responsibility of TCB components to ensure that a system behaves properly and
adheres to the security policy under all circumstances
,The part of the TCB that validates access to every resource prior to granting access requests is
called the - Answer Reference Monitor
The reference monitor may be a conceptual part of the TCB - Answer -It doesn't need to be an
actual, stand-alone system component
-The collection of components in the TCB that work together to implement reference monitor
functions is called the security kernel
The reference monitor requires - Answer descriptive information about each resource that it
protects
-Such information normally includes its classification and designation
The Bell-LaPadula and Biba models are both - Answer Information flow models
What is the difference between the Bell-LaPadula and Biba models - Answer -Bell-LaPadula is
concerned with preventing information from flowing from a high security level to a low security
level
-Biba is concerned with preventing information from flowing from a low security level to a high
security level
Techniques for Ensuring CIA? - Answer 1. Confinement
2. Bounds
3. Isolation
4. Controls
What is the Confinement technique for ensuring CIA? - Answer Process confinement allows a
process to read from and write to only certain memory locations and resources
enforced by the operating system
•If a process attempts to initiate an action beyond its granted authority, that action is denied
, •The authority level tells the OS how to set the bounds for a process (e.g. , the memory
addresses and resources it can access)
•These bounds can be either logical or physical
What is Isolation technique for ensuring CIA? - Answer -When a process is confined through
enforcing access bounds, that process runs in isolation
•Process isolation ensures that any behavior will affect only the memory and resources
associated with the isolated process
What is Control technique for ensuring CIA? - Answer -Controls use access rules to limit the
access by a subject to an object
The Biba model is also built on a state machine concept, and is characterized by two basic
properties - Answer 1. -The Simple Integrity Property states that a subject cannot read an
object at a lower integrity level (no read down)
-When integrity is important, you do not want unvalidated data read into validated documents
•The potential for data contamination is too great to permit such access
2. -The * (star) Integrity Property states that a subject cannot modify an object at a higher
integrity level (no write up)
-A subject cannot write to an object at a higher integrity level
What are Closed Systems? - Answer -Designed to work with a narrow range of other systems,
generally all from the same manufacturer
Standards for closed systems are often proprietary and not normally disclosed
What is an Open System? - Answer -Designed using agreed-upon industry standards
•Much easier to integrate with systems from different manufacturers
There is also a distinction between open-source and closed-source systems - Answer -In open-
source solutions source code and internal logic are exposed to the public
•Dependent upon public inspection / review to improve the product over time
-In closed-source (or commercial) solutions source code and internal logic are hidden from the
