Computer Networking and Security Module
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Questions and Answers

What is the purpose of authentication?

proving a claim - usually that you are who you say you are

What are the two types of attackers as mentioned in the content?

  • Amateurs and Script Kiddies
  • Hackers and Crackers (correct)
  • Career Criminals and State-supported Spies
  • Opportunistic Attackers and Inside Attackers

    • Cryptanalysis is the process of breaking an encrypted ____.

    code

    Principle of Least Privilege states to give more privileges than necessary for a job.

    <p>False</p> Signup and view all the answers

    Match the cryptographic term with its definition:

    <p>Plaintext = original form of a message Ciphertext = coded/encrypted form of a message Cipher = encryption method or process Key = info used in cipher known only by the sender/receiver</p> Signup and view all the answers

    What is the primary goal of confidentiality in computer security?

    <p>Prevention of unauthorized disclosure of information.</p> Signup and view all the answers

    What is the main purpose of integrity in computer security?

    <p>Preventing unauthorized writing or modification of information.</p> Signup and view all the answers

    Define availability in the context of computer security.

    <p>Assures that systems work promptly and service isn't denied to authorized users.</p> Signup and view all the answers

    Which of the following are considered threat agents?

    <p>Hackers</p> Signup and view all the answers

    Non-repudiation in computer security prevents the denial of a transmitted message.

    <p>True</p> Signup and view all the answers

    What is the purpose of a digital signature algorithm?

    <p>Signing messages or data for authentication</p> Signup and view all the answers

    Which key is used by the sender in a digital signature procedure?

    <p>Private key</p> Signup and view all the answers

    Vulnerability Assessment is used to detect and resolve security problems.

    <p>True</p> Signup and view all the answers

    Hash functions transform variable-length messages into a __________ message digest.

    <p>fixed-length</p> Signup and view all the answers

    Match the following asymmetric key algorithms with their descriptions:

    <p>El Gamal = Developed by Taher ElGamal Diffie-Hellman Key Agreement (DH) = Key agreement protocol for sharing symmetric keys Digital Signature Algorithm (DSA) = Used for signing messages for authentication</p> Signup and view all the answers

    What is cryptology?

    <p>Cryptology is the field of study which deals with both cryptography and cryptanalysis.</p> Signup and view all the answers

    What does Cryptography classification include?

    <p>Classical/Conventional Cryptography and Modern Cryptography.</p> Signup and view all the answers

    Define Substitution Ciphers.

    <p>Substitution ciphers replace one symbol with another.</p> Signup and view all the answers

    Explain Monoalphabetic Ciphers.

    <p>Monoalphabetic ciphers involve a simple relationship between symbols in plaintext and ciphertext.</p> Signup and view all the answers

    In the Hill Cipher, the key matrix needs to have a ____________.

    <p>multiplicative inverse</p> Signup and view all the answers

    What is the rail-fence transposition used for?

    <p>Rail-fence transposition rearranges the order of letters in a plaintext message.</p> Signup and view all the answers

    Which are building blocks of security in modern cryptographic functions?

    <p>All of the above</p> Signup and view all the answers

    In asymmetric key cryptography, there are two keys: a private key and a public key.

    <p>True</p> Signup and view all the answers

    What is the commonly known application for Secure Shell (SSH)?

    <p>for remote login to computer systems by users.</p> Signup and view all the answers

    What are common applications of Secure Email?

    <p>Adding confidentiality and integrity protection to emails</p> Signup and view all the answers

    TLS-based client digital certificates are used in securing web servers. Is this statement true or false?

    <p>False</p> Signup and view all the answers

    Physical security protects hardware with ______________.

    <p>doors that lock</p> Signup and view all the answers

    Match the following firewall types with their descriptions:

    <p>Network firewalls = Filter traffic between two or more networks and run on network hardware Host-based firewalls = Run on host computers and control network traffic in and out of those machines Application-Level Gateway (application firewall / proxy server) = Runs special software that acts as a proxy for a service request</p> Signup and view all the answers

    Study Notes

    Introduction to Computer Security

    • The practice of assuring information and managing risks related to the use, processing, storage, and transmission of information or data.
    • Includes protection of the integrity, availability, authenticity, non-repudiation, and confidentiality of user data.

    Information Assurance (IA)

    • Measures that protect and defend information and information systems by ensuring their availability, integrity, authentication, confidentiality, and non-repudiation.
    • A superset of information security, strongly related to the field of information security, and also includes business continuity.

    Importance of Information Assurance

    • To protect information exchanges between interconnected computer systems.
    • To add business benefit through the use of IRM (Information Risk Management).
    • To minimize risk and ensure business continuity.

    Pillars of Information Assurance

    • Confidentiality: preserving authorized restrictions on access and disclosure.
    • Integrity: protecting against improper information modification or deletion.
    • Availability: ensuring timely and reliable access to and use of information.

    Security Models

    • Information security models: CIA triad (Confidentiality, Integrity, and Availability).
    • Other security models: Enterprise security, Cyber defense, and IA.

    Threats, Vulnerabilities, and Risk

    • Threat: any circumstances or events that can potentially harm an information system.
    • Vulnerability: weaknesses or faults in an information system or its components that could be exploited.
    • Risk: an expectation of loss expressed as the probability that a particular threat will exploit a particular vulnerability.

    Controls and Countermeasures

    • A control, safeguard, or countermeasure is an action, device, procedure, or technique that reduces a threat, vulnerability, or attack.
    • Examples of controls: access controls, encryption, firewalls, and intrusion detection systems.

    Types of Attacks

    • Active attack: an attempt to alter or affect system resources or their operation.
    • Passive attack: an attempt to learn or make use of information from the system without affecting its operation.
    • Insider attack: initiated by an entity inside the security perimeter.
    • Outsider attack: initiated from outside the perimeter.

    Principles of Computer Security

    • Principle of Easiest Penetration

    • Principle of Adequate Protection

    • Principle of Effectiveness

    • Principle of Weakest Link

    • Principle of Least Privilege

    • Defense in Depth

    • Minimization

    • Compartmentalization

    • Keep Things Simple

    • Fail Securely

    • Balancing Security and Access### Cryptography Fundamentals

    • Cryptography concerns: Confidentiality, Integrity, Non-repudiation, and Authentication

    • Types of Malicious Attacks:

      • Logic bomb
      • Backdoor/Trapdoor
      • Adware
      • Flooders (DoS client)
      • Key loggers
      • Rootkit
      • Spam/scam, identity theft, e-payment frauds

    Cryptography Classifications

    • Classical/Conventional Cryptography: Substitution Ciphers and Transposition Ciphers
    • Modern Cryptography: Symmetric key cryptography and Public key cryptography

    Basic Cryptographic Terms

    • Plaintext: The original form of a message
    • Ciphertext: The coded/encrypted form of a message
    • Cipher: An encryption method or process
    • Key: Information used in a cipher known only by the sender/receiver
    • Symmetric Algorithm: Uses the same key for encryption and decryption
    • Asymmetric Algorithm: Uses different keys for encryption and decryption

    Substitution Ciphers

    • Monoalphabetic Ciphers: One symbol in the plaintext corresponds to one symbol in the ciphertext
    • Polyalphabetic Ciphers: One symbol in the plaintext corresponds to multiple symbols in the ciphertext
    • Examples of Substitution Ciphers: Caesar Cipher, Vigenere Cipher, Hill Cipher

    Transposition Ciphers

    • Reorders the symbols in the plaintext
    • Types of Transposition Ciphers:
      • Keyless Transposition Ciphers
      • Keyed Transposition Ciphers
    • Examples of Transposition Ciphers: Rail-fence Transposition, Columnar Transposition

    Symmetric Key Cryptography

    • Uses the same key for encryption and decryption
    • Key Distribution Problem: Secure distribution of the secret key
    • Symmetric Cipher Model: Alice and Bob use the same key for encryption and decryption
    • Examples of Symmetric Key Algorithms: DES, 3DES, AES

    Asymmetric Key Cryptography (Public Key Cryptography)

    • Uses different keys for encryption and decryption
    • Key Pair: A public key and a private key
    • Advantages: Simpler and faster, eliminates the key distribution problem
    • Examples of Asymmetric Key Algorithms: RSA, Diffie-Hellman (DH)

    Diffie-Hellman (DH) Key Agreement

    • Used for key exchange
    • Key Agreement Process: Alice and Bob agree on a shared symmetric key without actually exchanging the key
    • Used in Internet Key Exchange (IKE) protocol and IP Security (IPSEC) architecture

    RSA (Rivest, Shamir, Adleman)

    • Asymmetric Key Algorithm
    • Uses the difficulty of factoring large numbers and discrete logarithm problem
    • Key Generation: Alice and Bob generate their own public and private keys### RSA Algorithm
    • Developed by Ron Rivest, Adi Shamir, and Len Adleman
    • Advantages: more secured, Authentication, and Variable Key Size (512, 1024, or 2048 bits)
    • Disadvantages: relatively complex
    • Used for the management of public key and distribution of digital certificates
    • Authenticates users and devices in the digital world
    • Most popular public key algorithm
    • Based on the principle that no mathematical method can efficiently find the prime factors of large numbers

    How RSA Works

    • Key Generation, Encryption & Decryption Procedure:
      • Choose two large prime numbers p and q
      • Compute n=pq and z=(p-1)(q-1)
      • Choose number e, less than n, which has no common factor (other than 1) with z
      • Find number d, such that ed – 1 is exactly divisible by z
      • Keys are generated using n, d, e
      • Public key is (n,e)
      • Private key is (n, d)
    • Encryption: c = me mod n
    • Decryption: m = cd mod n

    Other Asymmetric Key Algorithms

    • El Gamal:
      • Developed by Taher ElGamal
      • Variable key size (512 or 1024 bits)
      • Less common than others
    • Diffie-Hellman Key Agreement (DH):
      • Key exchange protocol
    • Digital Signature Algorithm (DSA):
      • Used for digital signatures
      • Relies on public key cryptography
      • Private key is used for signing, and public key is used for verifying signatures

    Hash Functions

    • A hash function takes a variable-size message as input and produces a fixed-size output (hash code or message digest)
    • No key is used in this algorithm
    • Fixed-length hash value is computed as per the plain text
    • Used in many operating systems to encrypt passwords
    • Creates a unique, fixed-length signature for a specific message or data set

    Vulnerability and Penetration Testing

    • Vulnerability: a weakness or flaw in the system security that may result in unauthorized access
    • Vulnerability Assessment: the process of scanning the system to identify vulnerabilities
    • Penetration Testing: an authorized simulated attack on a computer system to evaluate the security of the system
    • Types of vulnerability scanners:
      • Host-Based: identifies issues in the host or system
      • Network-Based: detects open ports and identifies unknown services running on these ports
      • Database-Based: identifies security exposure in database systems to prevent SQL Injections

    Secure Web Servers and Firewalls

    • Secure Web Servers:
      • Adds confidentiality and integrity protection to ordinary e-mail
      • Examples: PGP
    • Firewalls:
      • A program or network device that filters access to a protected network from the internet connection
      • Monitors and controls incoming and outgoing network traffic
      • Objectives:
        • Keep intruders, malicious code, and unwanted traffic out
        • Keep private and sensitive information in
      • Categories:
        • Network Firewalls: filter traffic between two or more networks and run on network hardware
        • Host-Based Firewalls: run on host computers and control network traffic in and out of those machines
        • Application-Level Gateway (Application Firewall/Proxy Server): runs special software that acts as a proxy for a service request

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    Description

    This quiz covers data communication, computer networking, network and system administration, and computer security, as part of the Computer Science program at Addis Ababa University.

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