Introduction to Operating System | NPTEL | Week 8 Answers

This set of MCQ(multiple choice questions) focuses on the Introduction to Operating System Week 8 Answers

You should practice these questions to improve fundamentals of Cyber security needed for various interviews (like company interview, campus interview, walk-in interview), entrance exams, placements and other competitive exams. All the questions in this particular section are based on only “Introduction to Operating System Week 8 Answers“.

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Week 1: Assignment solutions
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Week 3:
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Week 4: Assignment solutions

Week 5: Assignment Solutions
Week 6: Assignment solutions
Week 7: Assignment solutions
Week 8: Assignment solutions
Week 9: Assignment solutions
Week 10: Assignment solutions
Week 11: Assignment solutions
Week 12: Assignment solutions

NOTE: You can check your answer immediately by clicking show answer button. Moreover, this set of Introduction to Operating System Week 8 Answers” contains 10 questions.

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Introduction to Operating System Week 8 Answers

Q1. Suppose a source code has buffer overflow vulnerabilities. Which of the following can cause buffer overflow vulnerabilities
a. scanf(“%s”,…)
b. strcpy(destination,source)
c. send command used for network connection

a) Only A
b) B and C
c) A and B
d) All of the above

Answer: c) A and B

Introduction to Operating System Week 8 Answers

Q2. The non executable stack helps to prevent buffer overflow attack, but the overhead for making a stack as non executable stack is more than that of canaries.

a) True
b) False

Answer: a) True

Q3. Arrange the following, based on the order the parameters are pushed into the stack
a. Return address is pushed
b. The function call parameters
c. Previous frame pointers
d. Local variables are allocated

a) a, b, c, d
b) b, c, d, a
c) b, a, c, d
d) a, c, d, b

Answer: a) a, b, c, d

Introduction to Operating System Week 8 Answers

Q4. User X has found that s source code has a buffer overflow vulnerability caused by strcpy instruction. He then used strncpy in place of strcpy to prevent buffer overflow vulnerabilities. Which of the following is True

a) Buffer overflow attack will not occur in this source code
b) Buffer overflow vulnerabilities caused due to strcpy is avoided to some extend since it do the bound check
c) This will not make any change in the source code
d) None of these

Answer: b)

Introduction to Operating System Week 8 Answers

Q5. The number of gadgets present in the implementation depends on the number of C3 instruction in the machine code

a) True
b) False

Answer: b) False

Introduction to Operating System Week 8 Answers

Q6. Match the following
a Gadget 1) pseudo random number which detect the buffer overflow
b. Canaries 2) Short sequence of instruction ends with return
c. Shellcode 3) Execute inside the stack
d. ASLR 4) Specific address location

a) a-4, b-3, c-2, d-1
b) a-2, b-1, c-4, d-3
c) a-1, b-2, c-4, d-3
d) a-2, b-1 c-3, d-4

Answer: d) a-2, b-1 c-3, d-4

Q7. ASLR randomizes

a) The size of all arrays, thereby making it difficult to perform buffer overflows
b) All instructions in the program
c) Positions of the stack, heap, and libraries
d) Position of all variables in the stack

Answer: c) Positions of the stack, heap, and libraries

Introduction to Operating System Week 8 Answers

Q8. Match the following:
a. Secrecy 1)Limit the resource usage
b. Integrity 2)Unauthorized modification
c. Availability 3)Unauthorized disclosure

a) a-1, b-2, c-3
b) a-2, b-3, c-1
c) a-3, b-2, c-1
d) None of these

Answer: c) a-3, b-2, c-1

Introduction to Operating System Week 8 Answers

Q9. Consider the following commands in a system that supports discretionary access control.
Which one of the following statements is TRUE?
A. There is no leakage of rights due to these commands
B. A leakage may occur when a user with write permissions, executes ADD_READ command
C. A leakage may occur when a user with write permissions, executes ADD_DELETE command

a) Only A is correct
b) Only B is correct
c) Only C is correct
d) Both B and C is correct

Answer: b) Only B is correct

Q10. Suppose in a system you have 2000 files and 4 user, who has access rights on these files. Which on of the following will be the best method to implement access control ?

a) Using an authorization table
b) Using a capability based implementation
c) Using access control lists
d) Any of the above would techniques would work well

Answer: d) Any of the above would techniques would work well

Introduction to Operating System Week 8 Answers

Q11. Which of the following is False for the Information flow policies

a) Information can only flow from one security class to another is less secure
b) Information can flow from a lower class to a higher class is less secure
c) Combine information from a lower class with a higher class will result in a higher class is less secured
d) Combine information from one class with another information from another class will result in same class is more secure

Answer: c) Combine information from a lower class with a higher class will result in a higher class is less secured

Q12. In mandatory access control, information from top secret object will not flow to secret and vice versa.

a) True
b) False

Answer: a) True

Introduction to Operating System Week 8 Answers

Q13. A user X with secret clearance decides to transfer information to a third party Y. And Y tries to make changes in the confidential class. This breach of information can be prevented by _________________.

a) Implementing access control matrix
b) Implementing Bell-laPadula model
c) Implementing the Biba Model
d) None of the above

Answer: b) Implementing Bell-laPadula model

Q14. Using a Biba model, a user X can read a file Y and can write a file Z. Which of the following is TRUE?
A. X has clearance Confidential, Y is a Top Secret file and Z is a confidential file
B. X has secret Confidential, Y is a Unclassified File and Z is a confidential file
C. X has secret Confidential, Y is a secret file and Z is a confidential file

a) A and C are TRUE
b) B and C are TRUE
c) A and B are TRUE
d) Only A is TRUE

Answer: a) A and C are TRUE

Introduction to Operating System Week 8 Answers

Q15. In a company, there are 4 levels of employees: Top management, group-leaders, team-leaders, and staff. The top management takes feedback from all leaders employees and then creates new policy document from the company. The new document should be classified ________________.

a) A top management document
b) A team-leader document
c) A staff document
d) A public document

Answer: a) A top management document

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