1Which of the following creates a situation where a set of processes are blocked because each process is holding a resource and waiting for another resource acquired by some other process?
A.Starvation
B.Deadlock
C.Synchronization
D.Aging
Correct Answer: Deadlock
Explanation:Deadlock is a situation where a set of processes are blocked because each process is holding a resource and waiting for another resource acquired by some other process.
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2According to the Coffman conditions, which of the following is NOT a necessary condition for a deadlock to occur?
A.Mutual Exclusion
B.Hold and Wait
C.Preemption
D.Circular Wait
Correct Answer: Preemption
Explanation:No Preemption is the necessary condition. If resources can be preempted (taken away), deadlock can be broken. Therefore, the existence of 'Preemption' prevents deadlock.
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3In a Resource Allocation Graph (RAG), if the graph contains no cycles, which of the following statements is true?
A.A deadlock exists
B.No deadlock exists
C.The system is in an unsafe state
D.Starvation is occurring
Correct Answer: No deadlock exists
Explanation:If a resource allocation graph contains no cycles, then no deadlock exists in the system. A cycle is a necessary condition for deadlock.
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4The strategy of ignoring the problem of deadlock altogether and pretending that deadlocks never occur in the system is known as:
A.Banker's Algorithm
B.Ostrich Algorithm
C.Deadlock Avoidance
D.Deadlock Prevention
Correct Answer: Ostrich Algorithm
Explanation:The Ostrich Algorithm is a strategy of ignoring potential problems (like deadlocks) on the basis that they are extremely rare.
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5To prevent Hold and Wait, which of the following protocols can be used?
A.Processes must request resources in a strictly increasing order
B.Processes must request and be allocated all resources before execution
C.Resources can be preempted from processes
D.Resources are virtualized
Correct Answer: Processes must request and be allocated all resources before execution
Explanation:To prevent Hold and Wait, a process must guarantee that when it requests a resource, it does not hold any other resources. One protocol is to require a process to request and be allocated all its resources before it begins execution.
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6Deadlock Avoidance algorithms require the operating system to have which of the following information in advance?
A.The maximum number of resources of each type that each process may need
B.The exact order of execution
C.The priority of all processes
D.The password for every user
Correct Answer: The maximum number of resources of each type that each process may need
Explanation:Deadlock avoidance algorithms, such as the Banker's Algorithm, require that each process declare the maximum number of resources of each type that it may need.
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7In the context of the Banker's Algorithm, a state is considered safe if:
A.There exists a cycle in the resource allocation graph
B.There exists a sequence of all processes such that each process can satisfy its maximum demand
C.All resources are currently free
D.No process is waiting for resources
Correct Answer: There exists a sequence of all processes such that each process can satisfy its maximum demand
Explanation:A state is safe if the system can allocate resources to each process (up to its maximum) in some order (safe sequence) and still avoid a deadlock.
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8Given processes through , the Banker's Algorithm uses several data structures. If is the maximum demand and is the amount currently allocated, how is calculated?
A.
B.
C.
D.
Correct Answer:
Explanation:The matrix represents the remaining resource needs of each process. It is calculated as the Maximum demand minus the resources currently Allocated.
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9Which data structure is typically used for deadlock detection in a system with only a single instance of each resource type?
A.Resource Allocation Graph
B.Wait-for Graph
C.Gantt Chart
D.Access Matrix
Correct Answer: Wait-for Graph
Explanation:If each resource type has a single instance, a Wait-for graph can be used. A deadlock exists if and only if there is a cycle in the Wait-for graph.
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10When recovering from a deadlock by process termination, what is a primary criterion for selecting a 'victim' process?
A.The process name
B.The amount of CPU time the process has used so far (cost of rollback)
C.The time of day
D.The size of the process name
Correct Answer: The amount of CPU time the process has used so far (cost of rollback)
Explanation:Selection of a victim involves minimizing cost. Factors include the priority of the process, how long it has computed, and how many resources it has used.
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11What is the phenomenon called where a process waits indefinitely for a resource because other processes are constantly preempting it or having higher priority?
A.Deadlock
B.Livelock
C.Starvation
D.Protection
Correct Answer: Starvation
Explanation:Starvation (or indefinite blocking) is a situation where a process waits indefinitely within the semaphore or wait queue because other processes are continuously preferred.
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12Which technique helps in solving the problem of Starvation?
A.Mutual Exclusion
B.Aging
C.Hold and Wait
D.Spoofing
Correct Answer: Aging
Explanation:Aging involves gradually increasing the priority of processes that wait in the system for a long time, ensuring they eventually get executed.
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13In the context of Operating Systems, what is the primary difference between Protection and Security?
A.Protection deals with internal threats; Security deals with external threats
B.Protection handles external attacks; Security handles access rights
C.There is no difference
D.Protection is for hardware; Security is for software
Correct Answer: Protection deals with internal threats; Security deals with external threats
Explanation:Protection refers to a mechanism for controlling access of programs, processes, or users to system resources (internal control). Security is the measure of confidence that the integrity of a system and its data will be preserved (often against external threats).
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14The Principle of Least Privilege dictates that:
A.Users should be given the highest level of access by default
B.Programs, users, and systems should be given just enough privileges to perform their task
C.Security mechanisms should be complex to deter attackers
D.All users should have administrator rights
Correct Answer: Programs, users, and systems should be given just enough privileges to perform their task
Explanation:The principle of least privilege states that a subject should be given only those privileges that it needs in order to complete its task.
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15A protection domain specifies:
A.A set of users
B.A set of objects and the operations that may be performed on those objects
C.A list of passwords
D.The physical location of the server
Correct Answer: A set of objects and the operations that may be performed on those objects
Explanation:A domain is a set of access rights, where each access right is an ordered pair <object-name, rights-set>.
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16In an Access Matrix model, the rows represent __ and the columns represent __.
A.Objects, Domains
B.Domains, Objects
C.Users, Passwords
D.Files, Processes
Correct Answer: Domains, Objects
Explanation:In an Access Matrix, the rows represent domains (or subjects), and the columns represent objects (files, printers, etc.). The entry defines the set of operations that a process executing in Domain can invoke on Object .
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17Which implementation of the Access Matrix corresponds to storing the non-empty entries of the matrix by column (associating permissions with the object)?
A.Capability Lists
B.Access Control Lists (ACL)
C.Global Table
D.Lock-Key Mechanism
Correct Answer: Access Control Lists (ACL)
Explanation:An ACL is associated with an object (column) and lists all the domains that can access that object and how.
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18A Capability List is associated with:
A.Each Object
B.Each Domain (Process)
C.The Operating System Kernel only
D.The Network Interface
Correct Answer: Each Domain (Process)
Explanation:A Capability List is a list of objects together with the operations allowed on those objects, associated with a specific domain (row-wise decomposition of the Access Matrix).
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19What is a Buffer Overflow vulnerability?
A.When a process writes more data to a fixed-length buffer than the buffer can hold
B.When the CPU cache fills up
C.When the network bandwidth is exceeded
D.When a disk runs out of space
Correct Answer: When a process writes more data to a fixed-length buffer than the buffer can hold
Explanation:Buffer overflow occurs when a program attempts to write more data to a buffer than it is allocated, overwriting adjacent memory locations, often the return address in the stack.
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20A code segment embedded in a legitimate program that is designed to 'explode' or execute a malicious function when certain conditions are met is called a:
A.Virus
B.Logic Bomb
C.Worm
D.Trap Door
Correct Answer: Logic Bomb
Explanation:A Logic Bomb is code embedded in a legitimate program that is set to 'explode' (execute malicious actions) when certain conditions (like a specific date or time) are met.
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21A Trapdoor (or Backdoor) is:
A.A hardware failure
B.A method of bypassing normal authentication methods
C.A type of firewall
D.A physical lock on a server room
Correct Answer: A method of bypassing normal authentication methods
Explanation:A trapdoor (or backdoor) is a secret entry point into a program that allows someone who is aware of the trapdoor to gain access without going through the usual security access procedures.
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22Which of the following describes a Trojan Horse?
A.A self-replicating program that spreads over a network
B.A program that appears useful but contains hidden malicious code
C.A technique to guess passwords
D.A denial of service attack
Correct Answer: A program that appears useful but contains hidden malicious code
Explanation:A Trojan Horse is a malicious program that misleads users of its true intent by appearing to be a legitimate or useful program.
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23What distinguishes a Worm from a Virus?
A.A worm requires a host program to spread, a virus does not
B.A worm is a standalone program that replicates itself over a network; a virus attaches to a host program
C.A worm only attacks hardware
D.There is no difference
Correct Answer: A worm is a standalone program that replicates itself over a network; a virus attaches to a host program
Explanation:Viruses are code fragments that attach to legitimate programs (hosts). Worms are standalone programs that use computer networks to replicate themselves to other nodes.
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24In Password-based Authentication, what is the purpose of 'salting' the password?
A.To make the password shorter
B.To ensure that the same password results in different hash values
C.To encrypt the connection
D.To allow the user to see the password
Correct Answer: To ensure that the same password results in different hash values
Explanation:A salt is a random string added to the password before hashing. It prevents dictionary attacks and ensures that two users with the same password have different stored hashes.
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25Which attack involves an attacker sitting between two communicating parties and intercepting/modifying the data?
A.Denial of Service
B.Man-in-the-Middle (MitM)
C.Phishing
D.Buffer Overflow
Correct Answer: Man-in-the-Middle (MitM)
Explanation:In a Man-in-the-Middle attack, the attacker secretly relays and possibly alters the communication between two parties who believe they are directly communicating with each other.
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26Cache Poisoning typically affects which network service?
A.DNS (Domain Name System)
B.FTP (File Transfer Protocol)
C.SSH (Secure Shell)
D.Telnet
Correct Answer: DNS (Domain Name System)
Explanation:Cache Poisoning (specifically DNS cache poisoning) involves introducing corrupt data into the DNS resolver's cache, causing the name server to return an incorrect IP address.
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27A Denial of Service (DoS) attack aims to:
A.Steal sensitive data
B.Gain administrative access
C.Disrupt the legitimate use of a system or network
D.Encrypt user files
Correct Answer: Disrupt the legitimate use of a system or network
Explanation:The goal of a DoS attack is to make a machine or network resource unavailable to its intended users.
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28Which of the following is an example of Social Engineering?
A.Phishing
B.Port Scanning
C.Packet Sniffing
D.SQL Injection
Correct Answer: Phishing
Explanation:Phishing involves tricking individuals into revealing sensitive information (like passwords) by pretending to be a trustworthy entity, which relies on social manipulation (Social Engineering).
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29In the context of Deadlock Prevention, the condition of Circular Wait can be eliminated by:
A.Using semaphores
B.Defining a linear ordering of resource types
C.Using time-sharing
D.Allowing preemption
Correct Answer: Defining a linear ordering of resource types
Explanation:Circular wait can be prevented by imposing a total ordering of all resource types and requiring that each process requests resources in an increasing order of enumeration.
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30If a system is in an Unsafe State, it implies that:
A.A deadlock has definitely occurred
B.A deadlock may occur
C.The system will crash immediately
D.The system is secure
Correct Answer: A deadlock may occur
Explanation:An unsafe state means there is no guarantee that the system can prevent a deadlock. It does not mean a deadlock currently exists, but the potential is there.
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31What is Stack Smashing?
A.A method to compress the stack
B.A form of buffer overflow targeting the stack to modify the return address
C.Optimizing stack memory usage
D.Deleting the stack
Correct Answer: A form of buffer overflow targeting the stack to modify the return address
Explanation:Stack smashing is a specific type of buffer overflow attack where the attacker overwrites the stack memory, specifically the return address, to redirect execution to malicious code.
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32Which of the following is NOT a goal of protection?
A.Preventing malicious misuse of the system
B.Ensuring efficient use of resources
C.Enforcing usage policies
D.Increasing the clock speed of the CPU
Correct Answer: Increasing the clock speed of the CPU
Explanation:Goals of protection include preventing misuse, ensuring fair resource use, and enforcing policies. CPU clock speed is a hardware performance characteristic.
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33In the Lock-Key mechanism for implementing access rights:
A.Each object has a list of unique bit patterns (locks) and each domain has a list of unique bit patterns (keys)
B.Keys are public
C.Locks are managed by the user
D.It is identical to ACL
Correct Answer: Each object has a list of unique bit patterns (locks) and each domain has a list of unique bit patterns (keys)
Explanation:In this scheme, a process in a domain can access an object only if that domain has a key that matches one of the locks of the object.
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34Port Scanning is used by attackers to:
A.Physically steal a server
B.Identify which services are running on a target system
C.Encrypt a hard drive
D.Overheat the CPU
Correct Answer: Identify which services are running on a target system
Explanation:Port scanning involves sending messages to various ports on a computer to find out which services (ports) are open and listening, often as a precursor to an attack.
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35Which term describes a virus that changes its own code (signature) each time it infects a new host to avoid detection?
A.Polymorphic Virus
B.Macro Virus
C.Boot Sector Virus
D.Stealth Virus
Correct Answer: Polymorphic Virus
Explanation:A polymorphic virus encrypts its body and changes the decryption routine (signature) with every infection to evade antivirus detection based on static signatures.
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36What is the Confinement Problem in protection?
A.Ensuring a process cannot migrate to another CPU
B.Ensuring that information contained in an object does not leak outside the system
C.Keeping the CPU temperature low
D.Limiting the number of users
Correct Answer: Ensuring that information contained in an object does not leak outside the system
Explanation:The confinement problem is the problem of guaranteeing that a process (the server) which borrows a client's data does not record/leak that data to others.
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37In a resource allocation graph, a request edge is directed from:
A.Resource to Process
B.Process to Resource
C.Process to Process
D.Resource to Resource
Correct Answer: Process to Resource
Explanation:A request edge signifies that a process has requested an instance of resource type . It is drawn from to .
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38Which deadlock recovery method involves rolling back a process to a safe state and restarting it?
A.Process Termination
B.Resource Preemption
C.Prevention
D.Exclusion
Correct Answer: Resource Preemption
Explanation:When preempting resources to break a deadlock, the system must roll back the victim process to a safe state (often the beginning) and restart it.
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39In One-Time Password (OTP) systems, the security relies on:
A.The password being used only once and then becoming invalid
B.The password being extremely long
C.The password being the user's name
D.Biometrics only
Correct Answer: The password being used only once and then becoming invalid
Explanation:OTP systems generate a password valid for only one login session or transaction, preventing replay attacks.
Explanation:These are the three core goals of security: Confidentiality (secrecy), Integrity (correctness), and Availability (accessibility).
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41A Dumpster Diving attack involves:
A.Hacking into the recycle bin folder
B.Scavenging through physical trash to find sensitive information
C.Deleting files randomly
D.Overwriting memory buffers
Correct Answer: Scavenging through physical trash to find sensitive information
Explanation:Dumpster diving is a physical security threat where attackers look through trash for notes, printouts, or devices containing passwords or sensitive data.
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42Which of the following is a passive attack?
A.Packet Sniffing
B.Data Modification
C.Denial of Service
D.Masquerading
Correct Answer: Packet Sniffing
Explanation:Packet sniffing (traffic analysis) is a passive attack because the attacker monitors the transmission but does not alter the data or disrupt the communication.
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43With respect to Deadlock, what is Mutual Exclusion?
A.Processes must share resources simultaneously
B.At least one resource must be held in a non-sharable mode
C.All resources are sharable
D.No process can access any resource
Correct Answer: At least one resource must be held in a non-sharable mode
Explanation:Mutual exclusion means that only one process can use a specific resource instance at a time.
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44If a system has 3 processes and 4 instances of Resource R, and each process needs 2 instances of R to complete, will deadlock occur?
A.Yes, definitely
B.No, never
C.Maybe
D.Only if preemption is disabled
Correct Answer: No, never
Explanation:Total resources = 4. Max need per process = 2. Even if all 3 processes hold 1 resource (using 3 total), 1 resource remains free. This free resource can be allocated to one process to finish (reach 2), releasing its resources. Thus, deadlock is impossible.
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45Which of the following describes the Wait-for graph properly?
A.It is obtained by removing resource nodes and collapsing edges from the Resource Allocation Graph
B.It includes both process and resource nodes
C.It is used for multiple instances of resources
D.It shows the memory usage of processes
Correct Answer: It is obtained by removing resource nodes and collapsing edges from the Resource Allocation Graph
Explanation:A wait-for graph consists of nodes representing processes. An edge exists if is waiting for a resource held by .
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46In the Access Matrix, the Switch right allows:
A.A process to delete a domain
B.A process to switch from one domain to another
C.A process to switch off the computer
D.A process to edit a file
Correct Answer: A process to switch from one domain to another
Explanation:The switch right, when held by a domain on another domain, allows a process executing in the first domain to switch execution context to the second domain.
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47What is Spyware?
A.Software that encrypts files
B.Software that secretly gathers information about a user and sends it to a third party
C.Software that speeds up the computer
D.A type of firewall
Correct Answer: Software that secretly gathers information about a user and sends it to a third party
Explanation:Spyware is malicious software designed to enter your computer device, gather data about you, and forward it to a third-party without your consent.
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48What is the primary vulnerability exploited by a Zero-Day Attack?
A.Weak passwords
B.Unpatched software vulnerabilities unknown to the vendor
C.Physical theft
D.Phishing
Correct Answer: Unpatched software vulnerabilities unknown to the vendor
Explanation:A Zero-Day attack exploits a software vulnerability on the same day it becomes known (or before), meaning the developer has had 'zero days' to fix it.
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49Which of the following is an example of an Authentication mechanism?
A.Access Control List
B.Encryption
C.Biometrics (Fingerprint)
D.Firewall
Correct Answer: Biometrics (Fingerprint)
Explanation:Authentication validates identity. Biometrics, passwords, and smart cards are authentication mechanisms. ACLs are authorization mechanisms.
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50The Banker's Algorithm is applicable for:
A.Systems with single instance of each resource type
B.Systems with multiple instances of each resource type
C.Systems without resources
D.Network routing
Correct Answer: Systems with multiple instances of each resource type
Explanation:The Banker's Algorithm is designed for deadlock avoidance in systems where resources have multiple instances.
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