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Operating System MCQ Set 1

1. What is breach of integrity ?
a) This type of violation involves unauthorized reading of data
b) This violation involves unauthorized modification of data
c) This violation involves unauthorized destruction of data
d) This violation involves unauthorized use of resources

View Answer

Answer: b [Reason:] None.

2. What is breach of confidentiality ?
a) This type of violation involves unauthorized reading of data
b) This violation involves unauthorized modification of data
c) This violation involves unauthorized destruction of data
d) This violation involves unauthorized use of resources

View Answer

Answer: a [Reason:] None.

3. What is theft of service ?
a) This type of violation involves unauthorized reading of data
b) This violation involves unauthorized modification of data
c) This violation involves unauthorized destruction of data
d) This violation involves unauthorized use of resources

View Answer

Answer: d [Reason:] None.

4. What is breach of availability ?
a) This type of violation involves unauthorized reading of data
b) This violation involves unauthorized modification of data
c) This violation involves unauthorized destruction of data
d) This violation involves unauthorized use of resources

View Answer

Answer: c [Reason:] None.

5. What is Trojan horse ?
a) It is a useful way to encrypt password
b) It is a user which steals valuable information
c) It is a rogue program which tricks users
d) It’s a brute force attack algorithm

View Answer

Answer: c [Reason:] None.

6. What is trap door ?
a) IT is trap door in WarGames
b) It is a hole in software left by designer
c) It is a Trojan horse
d) It is a virus which traps and locks user terminal

View Answer

Answer: b [Reason:] None.

7. Which mechanism is used by worm process ?
a) Trap door
b) Fake process
c) Spawn Process
d) VAX process

View Answer

Answer: c [Reason:] None.

8. Which of the following is not a characteristic of virus ?
a) Virus destroy and modify user data
b) Virus is a standalone program
c) Virus is a code embedded in a legitimate program
d) Virus cannot be detected

View Answer

Answer: d [Reason:] Virus can be detected by having a antivirus program.

9. What is known as masquerading ?
a) When one participant in communication pretends to be someone else
b) When attacker modifies data in communication
c) When attack is of fraudulent repeat of a valid data
d) When attack gains access to remote systems

View Answer

Answer: a [Reason:] None.

10. Who unleashed famous worm attack in 1988 which effected UNIX systems and caused losses in millions ?
a) Robert Morris
b) Bob Milano
c) Mark zuckerberg
d) Bill Gates

View Answer

Answer: a [Reason:] None.

11. What is port scanning ?
a) It is a software used to scan system for attack
b) It is a software application designed to probe a server or host for open ports
c) It is software used to scan system for introducing attacks by brute force
d) None of the mentioned

View Answer

Answer: b [Reason:] None.

12. Which is not a port scan type ?
a) TCP scanning
b) SYN scanning
c) UDP scanning
d) SYSTEM Scanning

View Answer

Answer: d [Reason:] None.

13. Which is not a valid port scan type ?
a) ACK scanning
b) Window scanning
c) IGMP scan
d) FIN scanning

View Answer

Answer: c [Reason:] None.

14. What are zombie systems ?
a) Are specific system which are designed to attack by manufacturer
b) They are network of known hacking group
c) These systems are previously compromised, independent systems
d) None of the mentioned

View Answer

Answer: c [Reason:] None.

15. What is known as DOS attack ?
a) It is attack to block traffic of network
b) It is attack to harm contents stored in HDD by worm spawn processes
c) It is an attempt to make a machine or network resource unavailable
d) None of the mentioned

View Answer

Answer: c [Reason:] None.

16. With regard to DOS attack what is not true from below options ?
a) We can stop DOS attack completely
b) By upgrading OS vulnerability we can stop DOS attack to some extent
c) DOS attack has to be stopped at network level
d) Such attack can last for hours

View Answer

Answer: a [Reason:] None.

Operating System MCQ Set 2

1. What is not a important part of security protection ?
a) Large amount of RAM to support antivirus
b) Strong passwords
c) Audit log periodically
d) Scan for unauthorized programs in system directories

View Answer

Answer: a [Reason:] RAM has no effect on security of a system. System’s protection remains unchanged in increasing or decreasing amount of RAM.

2. What is used to protect network from outside internet access ?
a) A trusted antivirus
b) 24 hours scanning for virus
c) Firewall to separate trusted and untrusted network
d) Deny users access to websites which can potentially cause security leak

View Answer

Answer: c [Reason:] Firewall create a protective barrier to secure internal network. A antivirus can only detect harmful viruses but cannot stop illegal access by remote attacker.

3. What is best practice in firewall domain environment ?
a) Create two domain trusted and untrusted domain
b) Create strong policy in firewall to support different types of users
c) Create one Demiliatarized zone
d) Create two DMZ zones with one untrusted domain

View Answer

Answer: c [Reason:] All live servers or workstations are kept in a separate zone than inside and outside to enhance protection.

4. Which direction access cannot happen using DMZ zone by default ?
a) Company computer to DMZ
b) Internet to DMZ
c) Internet to company computer
d) Company computer to internet

View Answer

Answer: c [Reason:] Connection from internet are never allowed to directly access internal PCs but is routed through DMZ zone to prevent attacks.

5. What are two features of a tripwire file system ?
a) It is a tool to monitor file systems
b) It is used to automatically take corrective action
c) It is used to secure UNIX system
d) None of the mentioned

View Answer

Answer: a [Reason:] None.

6. How do viruses avoid basic pattern matchof antivirus ?
a) They are encrypted
b) They act with special permissions
c) They modify themselves
d) None of the mentioned

View Answer

Answer: c [Reason:] None.

7. How does an antivirus of today identify viruses ?
a) Previously known patterns
b) It can detect unknown patterns
c) It can take high priority to increase scanning speed
d) None of the mentioned

View Answer

Answer: a [Reason:] None.

8. What is known as sandbox ?
a) It is a program which can be molded to do desired task
b) It is program that is controlled or emulated section of OS
c) It is a special mode of antivirus
d) None of the mentioned

View Answer

Answer: b [Reason:] None.

9. What is are two safe computing practices ?
a) Not to open software from unknown vendors
b) Open and execute programs in admin level/root
c) Open and execute programs in presence of antivirus
d) None of the mentioned

View Answer

Answer: a [Reason:] Disgruntled employees have in past infected the master copies of software programs to do economic harm to the company.

Operating System MCQ Set 3

1. Which of the following are forms of malicious attack ?
a) Theft of information
b) Modification of data
c) Wiping of information
d) All of the mentioned

View Answer

Answer: d [Reason:] None.

2. What are common security threats ?
a) File Shredding
b) File sharing and permission
c) File corrupting
d) File integrity

View Answer

Answer: b [Reason:] Sharing and associated permissions are usual exploits which can compromised the system.

3. From the following, which is not a common file permission ?
a) Write
b) Execute
c) Stop
d) Read

View Answer

Answer: c [Reason:] None.

4. Which of the following is a good practice ?
a) Give full permission for remote transferring
b) Grant read only permission
c) Grant limited permission to specified account
d) Give both read and write permission but not execute

View Answer

Answer: c [Reason:] Limited access is a key method to circumvent unauthorized access and exploits.

5. What is not a good practice for user administration ?
a) Isolating a system after a compromise
b) Perform random auditing procedures
c) Granting privileges on a per host basis
d) Using telnet and FTP for remote access

View Answer

Answer: d [Reason:] Telnet and FTP are not encrypted and can be compromised.

6. Which of the following is least secure method of authentication ?
a) Key card
b) fingerprint
c) retina pattern
d) Password

View Answer

Answer: d [Reason:] Passwords can be be compromised more easily than to replicate a physical thing like key card, fingerprint or retina.

7. Which of the following is a strong password ?
a) 19thAugust88
b) Delhi88
d) !augustdelhi

View Answer

Answer: c [Reason:] It has a combination of Alphabet both capital and small along with number and special character. Thus always use complex password with combination of all these.

8. Why is one time password safe ?
a) It is easy to generated
b) It cannot be shared
c) It is different for every access
d) It is a complex enctypted password

View Answer

Answer: c [Reason:] One time password is safe since it is generated per access and thus cannot be brute forced or deduced.

9. What does Light Directory Access Protocol (LDAP) doesn’t store ?
a) Users
b) Address
c) Passwords
d) Security Keys

View Answer

Answer: b [Reason:] None.

10. What is characteristic of RADIUS system ?
a) It is essential for centralized encryption and authentication
b) It works on Network layer to deny access to unauthorized people
c) It provides centralized authentication mechanism via network devices
d) It’s a strong File access system

View Answer

Answer: c [Reason:] None.

11. Which happens first authorization or authentication ?
a) Authorization
b) Authentication
c) Authorization & Authentication are same
d) None of the mentioned

View Answer

Answer: a [Reason:] None.

12. What is characteristics of Authorization ?
a) RADIUS and RSA
b) 3 way handshaking with syn and fin
c) Multilayered protection for securing resources
d) Deals with privileges and rights

View Answer

Answer: d [Reason:] None.

13. What forces the user to change password at first logon ?
a) Default behavior of OS
b) Part of AES encryption practice
c) Devices being accessed forces the user
d) Account administrator

View Answer

Answer: d [Reason:] Its administrator’s job to ensure that password of the user remains private and is known only to user. But while making a new user account he assigns a random general password to give it to user. Thus even administrator cannot access a particular users account.

14. What is not a best practice for password policy ?
a) Deciding maximum age of password
b) Restriction on password reuse and history
c) Password encryption
d) Having change password every 2 years

View Answer

Answer: d [Reason:] Old passwords are more vulnerable to being misplaced or compromised. Passwords should be changed periodically to enhance security.

Operating System MCQ Set 4

1. An un-interruptible unit is known as :
a) single
b) atomic
c) static
d) none of the mentioned

View Answer

Answer: b [Reason:] None.

2. The TestAndSet instruction is executed :
a) after a particular process
b) periodically
c) atomically
d) none of the mentioned

View Answer

Answer: c [Reason:] None.

3. Semaphore is a/an _______ to solve the critical section problem.
a) hardware for a system
b) special program for a system
c) integer variable
d) none of the mentioned

View Answer

Answer: c [Reason:] None.

4. The two atomic operations permissible on semaphores are :
a) wait
b) stop
c) hold
d) none of the mentioned

View Answer

Answer: a [Reason:] None.

5. Spinlocks are :
a) CPU cycles wasting locks over critical sections of programs
b) Locks that avoid time wastage in context switches
c) Locks that work better on multiprocessor systems
d) All of the mentioned

View Answer

Answer: d [Reason:] None.

6. The main disadvantage of spinlocks is that :
a) they are not sufficient for many process
b) they require busy waiting
c) they are unreliable sometimes
d) they are too complex for programmers

View Answer

Answer: b [Reason:] None.

7. The wait operation of the semaphore basically works on the basic _______ system call.
a) stop()
b) block()
c) hold()
d) wait()

View Answer

Answer: b [Reason:] None.

8. The signal operation of the semaphore basically works on the basic _______ system call.
a) continue()
b) wakeup()
c) getup()
d) start()

View Answer

Answer: b [Reason:] None.

9. If the semaphore value is negative :
a) its magnitude is the number of processes waiting on that semaphore
b) it is invalid
c) no operation can be further performed on it until the signal operation is performed on it
d) none of the mentioned

View Answer

Answer: a [Reason:] None.

10. The code that changes the value of the semaphore is :
a) remainder section code
b) non – critical section code
c) critical section code
d) none of the mentioned

View Answer

Answer: c [Reason:] None.

11. The following program consists of 3 concurrent processes and 3 binary semaphores. The semaphores are initialized as S0 = 1, S1 = 0, S2 = 0.

Process P0
while(true)
{
wait(S0);
print '0';
release(S1);
release(S2);
}
 
Process P1
wait(S1);
release(S0);
 
Process P2
wait(S2);
release(S0);

How many times will P0 print ‘0’ ?
a) At least twice
b) Exactly twice
c) Exactly thrice
d) Exactly once

View Answer

Answer: a [Reason:] None.

12. Each process Pi, i = 0,1,2,3,……,9 is coded as follows :

repeat
 P(mutex)
 {Critical Section}
 V(mutex)
 forever

The code for P10 is identical except that it uses V(mutex) instead of P(mutex). What is the largest number of processes that can be inside the critical section at any moment (the mutex being initialized to 1)?
a) 1
b) 2
c) 3
d) None of the mentioned

View Answer

Answer: c [Reason:] Any one of the 9 processes can get into critical section after executing P(mutex) which decrements the mutex value to 0. At this time P10 can enter critical section by incrementing the value to 1. Now any of the 9 processes can enter the critical section by again decrementing the mutex value to 0. None of the remaining processes can get into their critical sections.

13. Two processes, P1 and P2, need to access a critical section of code. Consider the following synchronization construct used by the processes :

Process P1 :
while(true)
{
w1 = true;
while(w2 == true);
Critical section
w1 = false;
}
Remainder Section
 
Process P2 :
while(true)
{
w2 = true;
while(w1 == true);
Critical section
w2 = false;
}

Remainder Section
Here, w1 and w2 are shared variables, which are initialized to false. Which one of the following statements is TRUE about the above construct?
a) It does not ensure mutual exclusion
b) It does not ensure bounded waiting
c) It requires that processes enter the critical section in strict alternation
d) It does not prevent deadlocks, but ensures mutual exclusion

View Answer

Answer: d [Reason:] None.

Operating System MCQ Set 5

1. What will happen if a non-recursive mutex is locked more than once ?
a) Starvation
b) Deadlock
c) Aging
d) Signaling

View Answer

Answer: b [Reason:] If a thread which had already locked a mutex, tries to lock the mutex again, it will enter into the waiting list of that mutex, which results in deadlock. It is because no other thread can unlock the mutex.

2. A semaphore :
a) is a binary mutex
b) must be accessed from only one process
c) can be accessed from multiple processes
d) none of the mentioned

View Answer

Answer: c [Reason:] None.

3. The two kinds of semaphores are :
a) mutex & counting
b) binary & counting
c) counting & decimal
d) decimal & binary

View Answer

Answer: b [Reason:] None.

4. A mutex :
a) is a binary mutex
b) must be accessed from only one process
c) can be accessed from multiple processes
d) None of the mentioned

View Answer

Answer: b [Reason:] None.

5. At a particular time of computation the value of a counting semaphore is 7.Then 20 P operations and 15 V operations were completed on this semaphore.The resulting value of the semaphore is : (GATE 1987)
a) 42
b) 2
c) 7
d) 12

View Answer

Answer: b [Reason:] P represents Wait and V represents Signal. P operation will decrease the value by 1 everytime and V operation will increase the value by 1 everytime.

6. A binary semaphore is a semaphore with integer values :
a) 1
b) -1
c) 0.8
d) 0.5

View Answer

Answer: a [Reason:] None.

7. The following pair of processes share a common variable X :

Process A
int Y;
A1: Y = X*2;
A2: X = Y;   
 
Process B
int Z;
B1: Z = X+1;
B2: X = Z;

X is set to 5 before either process begins execution. As usual, statements within a process are executed sequentially, but statements in process A may execute in any order with respect to statements in process B.
How many different values of X are possible after both processes finish executing ?
a) two
b) three
c) four
d) eight

View Answer

Answer: c [Reason:] Here are the possible ways in which statements from A and B can be interleaved. A1 A2 B1 B2: X = 11 A1 B1 A2 B2: X = 6 A1 B1 B2 A2: X = 10 B1 A1 B2 A2: X = 10 B1 A1 A2 B2: X = 6 B1 B2 A1 A2: X = 12.

8. The program follows to use a shared binary semaphore T :

Process A  
int Y;            
A1: Y = X*2;      
A2: X = Y;        
signal(T);        
 
Process B
int Z;
B1: wait(T);
B2: Z = X+1;
X = Z;

T is set to 0 before either process begins execution and, as before, X is set to 5.
Now, how many different values of X are possible after both processes finish executing ?
a) one
b) two
c) three
d) four

View Answer

Answer: a [Reason:]The semaphore T ensures that all the statements from A finish execution before B begins. So now there is only one way in which statements from A and B can be interleaved: A1 A2 B1 B2: X = 11.

9. Semaphores are mostly used to implement :
a) System calls
b) IPC mechanisms
c) System protection
d) None of the mentioned

View Answer

Answer: b [Reason:] None.

10. Spinlocks are intended to provide ____ only.
a) Mutual Exclusion
b) Bounded Waiting
c) Aging
d) Progress

View Answer

Answer: b [Reason:] None.

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