Introduction To Operating Systems NPTEL Week 8 Assignment

                     

These are solution for Introduction To Operating Systems NPTEL Week 8 Assignment

Course Name: Introduction To Operating Systems

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Q1) ASLR randomizes the position of all variables in the stack and thereby making it difficult to perform buffer overflows.
a. True
b. False

Answer: a. True


Q2) Match the following
a)Gadget         1) pseudo random number which detects buffer overflow
b)Canaries        2) Short sequence of instructions ending in a return
c)Shellcode      3) May execute in the stack if the NX bit is disabled
d)ASLR            4) helps prevent ROP attacks

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: c. a-1, b-2, c-4, d-3


These are solution for Introduction To Operating Systems NPTEL Week 8 Assignment


Q3) How does the NX bit prevent buffer overflow attacks?
a. It prevents buffers from overflowing
b. It prevents certain code from executing in data segments
c. It prevents the return address in the stack being replaced by an arbitrary location
d. All of the above

Answer: d. All of the above


Q4) An ROP attack can potentially be detected at run-time by
a. Canaries
b. The number of return statements executed in the processor
c. The number of return statements present in the executable
d. By a non-executable stack

Answer: c. The number of return statements present in the executable


These are solution for Introduction To Operating Systems NPTEL Week 8 Assignment


Q5) In the Bell-Lapadula model, information from top secret object will not flow to secret clearance.
a. True
b. False

Answer: b. False


Q6) 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: d. None of the above


These are solution for Introduction To Operating Systems NPTEL Week 8 Assignment


Q7) Programmer X has found that the 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 vulnerabilities caused due to strcpy is avoided due to  bounds check
b. This will not make any changes in the source code
c. Buffer overflow attack will not occur in this source code
d. None of these

Answer: d. None of these


Q8) 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 an owner of an object, executes CONFERwrite command.
C.A leakage may occur when a user with write permissions, executes ADD_READ 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


These are solution for Introduction To Operating Systems NPTEL Week 8 Assignment


Q9) Your project manager asks you to ensure that a particular source code is free from buffer overflow vulnerabilities. Which of the following would you need to look out for.
a. scanf in the code
b. strcpy in the code
c. For loops that manipulate arrays
d. All of the above

Answer: b. strcpy in the code


These are solution for Introduction To Operating Systems NPTEL Week 8 Assignment


Q10) Arrange the following, based on the order  parameters are pushed onto 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: b) b, c, d, a


These are solution for Introduction To Operating Systems NPTEL Week 8 Assignment

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These are solution for Introduction To Operating Systems NPTEL Week 8 Assignment