CS 6238 Midterm Exam Up to Date
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Question 1 (Security Design Principles)
Which design principle states that a system should use only a small number of different
types of security enforcement mechanisms?
A) Least Privilege
B) Economy of Mechanism
C) Open Design
D) Fail-Safe Default
Correct Answer: B
Economy of Mechanism means designing a system with a small number of simple security
mechanisms. The more features a system has, the more ways an attacker can exploit it.
This principle reduces the attack surface by minimizing complexity .
Question 2 (Reference Monitor & TCB)
What are the three requirements of the Trusted Computing Base (TCB)?
A) Tamper-proof, complete mediation, correctness
B) Confidentiality, integrity, availability
C) Authentication, authorization, accounting
D) Isolation, virtualization, encryption
Correct Answer: A
The TCB must be tamper-proof (cannot be altered), provide complete mediation (every
access to a resource must go through it), and be correct (no vulnerabilities in its
implementation). The reference monitor enforces access control policy and must meet
these requirements .
,Question 3 (Bell-LaPadula Model)
In the Bell-LaPadula model, which rule states that a subject can only write to an object if
the object's label dominates the subject's label?
A) Simple Security Property
B) *-Property (Star Property)
C) Discretionary Security Property
D) Tranquility Property
Correct Answer: B
*The -Property (Star Property) is the "write up" rule: a subject S can only write to an object
O if O dominates S. This prevents a subject from leaking sensitive information to a lower
classification level. The Simple Security Property is the "read down" rule .
Question 4 (Biba Model)
The Biba model focuses on which aspect of security?
A) Confidentiality
B) Integrity
C) Availability
D) Non-repudiation
Correct Answer: B
*The Biba model focuses on integrity. It includes the Simple Integrity Axiom (no read
down) and the -Integrity Axiom (no write up). User levels can be low, medium, or high,
and low-level users cannot produce high-integrity data .
Question 5 (Access Control: ACL vs. C-List)
Which statement correctly compares Access Control Lists (ACLs) and Capability Lists (C-
Lists) regarding accountability?
A) C-Lists are better for accountability because permissions are stored with the user
B) ACLs are better for accountability because you can find all users with permissions by
examining the object
,C) Both provide equal accountability
D) Neither provides accountability
Correct Answer: B
ACLs are better for accountability: to find all people with permissions for an object, you
look at the object's ACL. C-Lists are better for overhead of checking permission because
the user simply holds their permissions (like a ticket), which is more efficient than checking
a list .
Question 6 (x86 Privilege Levels)
In x86 architecture, what does CPL (Current Privilege Level) represent?
A) The privilege level of the data segment being accessed
B) The DPL of the code segment being executed
C) The privilege level stored in the segment selector
D) The page protection level
Correct Answer: B
CPL is the DPL of the code segment currently being executed. It indicates the privilege
level at which the processor is currently operating. Protection levels go from 0 to 3, where
0 is most privileged (kernel mode) .
Question 7 (x86 Protection Mechanisms)
What are the two hardware mechanisms the processor provides for isolating the TCB
from applications?
A) Encryption and hashing
B) Processor execution modes (privilege levels) and privileged instructions
C) Virtual memory and paging
D) Interrupts and exceptions
Correct Answer: B
Hardware provides two mechanisms: processor execution modes (privilege levels 0-3) and
privileged instructions that can only be executed in the most privileged mode (ring 0).
These prevent user-mode code from directly accessing kernel resources .
, Question 8 (Virtualization)
What distinguishes paravirtualization from full virtualization?
A) Paravirtualization requires no modifications to the guest OS
B) Paravirtualization requires the guest OS to be aware it is not running in ring 0 and to
be modified
C) Full virtualization is always faster than paravirtualization
D) Paravirtualization does not use a hypervisor
Correct Answer: B
Paravirtualization occurs when all requirements of a Virtual Machine Monitor (VMM) are
not met (i.e., transparency is not achieved). The guest OS is aware it is not running in ring
0 and must be modified to make hypercalls. Full virtualization provides complete
transparency without guest modifications .
Question 9 (Rowhammer)
What is the Rowhammer bug?
A) A vulnerability in the CPU cache that allows privilege escalation
B) A DRAM vulnerability where repeated reads of adjacent rows can cause bit flips in
memory
C) A virtualization escape that allows guest-to-host breakout
D) A password hashing weakness
Correct Answer: B
Rowhammer exploits a vulnerability in DRAM memories that can result in a bit flip in a
memory location by repeatedly reading locations in an adjacent row. This hardware-level
attack can compromise security by altering memory contents .
Question 10 (Password Hardening)
What is password hardening based on keystroke dynamics?
A) Encrypting passwords with AES-256
B) Combining what you know (password) with what you are (typing pattern) by
measuring key press durations and inter-key latencies
C) Requiring longer passwords
D) Storing passwords in a hardware security module
2025/2026 Latest Exam Questions And
Answers Complete Study Guide Exam.Instant
Pdf Download
Question 1 (Security Design Principles)
Which design principle states that a system should use only a small number of different
types of security enforcement mechanisms?
A) Least Privilege
B) Economy of Mechanism
C) Open Design
D) Fail-Safe Default
Correct Answer: B
Economy of Mechanism means designing a system with a small number of simple security
mechanisms. The more features a system has, the more ways an attacker can exploit it.
This principle reduces the attack surface by minimizing complexity .
Question 2 (Reference Monitor & TCB)
What are the three requirements of the Trusted Computing Base (TCB)?
A) Tamper-proof, complete mediation, correctness
B) Confidentiality, integrity, availability
C) Authentication, authorization, accounting
D) Isolation, virtualization, encryption
Correct Answer: A
The TCB must be tamper-proof (cannot be altered), provide complete mediation (every
access to a resource must go through it), and be correct (no vulnerabilities in its
implementation). The reference monitor enforces access control policy and must meet
these requirements .
,Question 3 (Bell-LaPadula Model)
In the Bell-LaPadula model, which rule states that a subject can only write to an object if
the object's label dominates the subject's label?
A) Simple Security Property
B) *-Property (Star Property)
C) Discretionary Security Property
D) Tranquility Property
Correct Answer: B
*The -Property (Star Property) is the "write up" rule: a subject S can only write to an object
O if O dominates S. This prevents a subject from leaking sensitive information to a lower
classification level. The Simple Security Property is the "read down" rule .
Question 4 (Biba Model)
The Biba model focuses on which aspect of security?
A) Confidentiality
B) Integrity
C) Availability
D) Non-repudiation
Correct Answer: B
*The Biba model focuses on integrity. It includes the Simple Integrity Axiom (no read
down) and the -Integrity Axiom (no write up). User levels can be low, medium, or high,
and low-level users cannot produce high-integrity data .
Question 5 (Access Control: ACL vs. C-List)
Which statement correctly compares Access Control Lists (ACLs) and Capability Lists (C-
Lists) regarding accountability?
A) C-Lists are better for accountability because permissions are stored with the user
B) ACLs are better for accountability because you can find all users with permissions by
examining the object
,C) Both provide equal accountability
D) Neither provides accountability
Correct Answer: B
ACLs are better for accountability: to find all people with permissions for an object, you
look at the object's ACL. C-Lists are better for overhead of checking permission because
the user simply holds their permissions (like a ticket), which is more efficient than checking
a list .
Question 6 (x86 Privilege Levels)
In x86 architecture, what does CPL (Current Privilege Level) represent?
A) The privilege level of the data segment being accessed
B) The DPL of the code segment being executed
C) The privilege level stored in the segment selector
D) The page protection level
Correct Answer: B
CPL is the DPL of the code segment currently being executed. It indicates the privilege
level at which the processor is currently operating. Protection levels go from 0 to 3, where
0 is most privileged (kernel mode) .
Question 7 (x86 Protection Mechanisms)
What are the two hardware mechanisms the processor provides for isolating the TCB
from applications?
A) Encryption and hashing
B) Processor execution modes (privilege levels) and privileged instructions
C) Virtual memory and paging
D) Interrupts and exceptions
Correct Answer: B
Hardware provides two mechanisms: processor execution modes (privilege levels 0-3) and
privileged instructions that can only be executed in the most privileged mode (ring 0).
These prevent user-mode code from directly accessing kernel resources .
, Question 8 (Virtualization)
What distinguishes paravirtualization from full virtualization?
A) Paravirtualization requires no modifications to the guest OS
B) Paravirtualization requires the guest OS to be aware it is not running in ring 0 and to
be modified
C) Full virtualization is always faster than paravirtualization
D) Paravirtualization does not use a hypervisor
Correct Answer: B
Paravirtualization occurs when all requirements of a Virtual Machine Monitor (VMM) are
not met (i.e., transparency is not achieved). The guest OS is aware it is not running in ring
0 and must be modified to make hypercalls. Full virtualization provides complete
transparency without guest modifications .
Question 9 (Rowhammer)
What is the Rowhammer bug?
A) A vulnerability in the CPU cache that allows privilege escalation
B) A DRAM vulnerability where repeated reads of adjacent rows can cause bit flips in
memory
C) A virtualization escape that allows guest-to-host breakout
D) A password hashing weakness
Correct Answer: B
Rowhammer exploits a vulnerability in DRAM memories that can result in a bit flip in a
memory location by repeatedly reading locations in an adjacent row. This hardware-level
attack can compromise security by altering memory contents .
Question 10 (Password Hardening)
What is password hardening based on keystroke dynamics?
A) Encrypting passwords with AES-256
B) Combining what you know (password) with what you are (typing pattern) by
measuring key press durations and inter-key latencies
C) Requiring longer passwords
D) Storing passwords in a hardware security module
