Computer Network Security – Flashcards
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Verifying that users are who they say they are and that each input arriving at the system came from a trusted source is
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Authentic
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A _______________ attack involves trying every possible key until an intelligible translation of the ciphertext is obtained.
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Brute Force
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If both parties use only one key over a secure encrypted channel, such a system is referred to as:
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Symmetric Encryption
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T/F A digital signature can guarantee the source but not the integrity of the message
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False
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X.509 defines the format for public-key certificates
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True
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Communication between end systems is encrypted using a
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Session Key
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What is an IPS
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An IPS blocks traffic
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Find the determinant mod of (A B) (C D)
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(A*D) - (B*C)
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What is the formula for finding the ciphertext C in rsa
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M^e Mod n
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What is the formula for finding the plaintext P in rsa
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C^d Mod n
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What is the formula for finding d
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de = 1 mod phi(n)
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T/F The most important development from the work on public Key encryption is the digital signature
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True
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The digital signature is formed by
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taking the hash of the message and encrypting the message with the creators private key
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X.509 is based on the use of
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Public Key cryptography and digital signatures
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What does TLS entail
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Transport Layer Security provides communications security over a computer network
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What does SSL entail
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Secure Socket Layer is the standard security technology for establishing an encrypted link between a web server and a browser
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Master key is
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Shared by the key distribution center and an end system or user and is used to encrypt the session key
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A nonce is
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A unique identifier, it needs to be hard to guess, such as a random number
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What is a passive threat
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Eavesdropping on, or monitoring transmissions
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What is an active security threat
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Modification, deletion, unauthorized access
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What are the four means of authenticating a user's identity
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Something the individual knows, possesses, is, does
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What are two common techniques used to protect a password file?
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Restrict access to the password file, Force users to select passwords that are difficult to guess.
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What is DAC
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Discretionary access control controls access based on identity.
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What is MAC
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Mandatory access control controls access based on comparing security labels
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What is a honeypot?
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Honeypots are decoy systems that are designed to lure a potential attacker away from critical systems.
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What are typical phases of operation of a virus or worm?
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A dormant phase, a propagation phase, a triggering phase, and an execution phase
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Define a denial of service (DOS) attack
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A denial of service attack is an action that prevents or impairs the network, system, or application
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Define a DDoS attack
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A Distributed Denial of Service attack uses multiple attacking systems, often using compromised user workstations or PCs
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What is an application-level gateway
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Also known as a proxy server, acts as a relay of application-level traffic
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Define Buffer Overflow
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A buffer overflow results from adding more information to a programs buffer than it was designed to hold
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What is a hello in a rail fence cipher
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hlo el
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What are the two ways to break a cipher
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Brute force, Cryptanalysis
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What are the 4 steps in AES
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Add round key, Substitute bytes, shift rows, Mix columns
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How is the hash value of a message encrypted?
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with a users private key
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What does EAP stand for
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Extensible authentication Protocol
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What is a stateful firewall
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watches traffic from end to end, it keeps track of the state of network connections, it knows if packets are fragmented
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What mechanisms can a virus use to conceal itself
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encryption, stealth, polymorphism, metamorphism
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What metrics are useful for profile based intrusion detection
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Solution counter, gauge, interval timer, resource utilization
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What are the two basic functions used in encryption algorithms
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Permutation and substitution
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what are the three broad categories of applications of public key cryptosystems
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Encryption/decryption, Digital signature, Key exchange
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What is a trap-door one-way function
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easy to calculate in one direction but unfeasible to calculate the other direction
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What is a MAC algorithm
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A message authentication code uses a secret key to calculate a code used for authentication
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What is salt
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salt is combined with the password at the input to the one-way encryption routine which results in a hash value
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List three design goals for a firewall
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All traffic must pass through the firewall, only authorized traffic is allowed to pass, the firewall is immune to penetration
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What is a weakness of a packet filtering firewall
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they don't examine upper layer data
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Why is it useful to have host-based firewalls
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Filtering rules can be tailored to the host environment, protection is provided independent of topology
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What is a DMZ network and what types of systems would you expect to find on such networks
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Between internal and external firewalls are one or more networked devices in a region referred to as a demilitarized zone
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What are three broad mechanisms that malware can use to propagate
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Infections of existing content, exploit of software vulnerabilities, social engineering attacks
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What is the difference between machine-executable and macro viruses?
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machine executable infect executable program files, macro viruses infect files with macro or scripting code
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What services are provided by the SSL Record Protocol
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Confidentiality, Message Integrity
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What steps are involved in the SSL record protocol transmission
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Fragmentation, compression, add MAC, encrypt, append ssl record header
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For what applications is SSH useful
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Providing a secure remote logon facility to replace TELNET
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What is NAC
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Network Access control, managing access to a network
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What is EAPOL
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EAP over LAN operates at the network layers and makes use of IEEE 802 LAN
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What is the function of IEEE 802.1X
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To provide access control functions for LANs
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What is a key distribution center
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a system is authorized to transmit temporary session keys to principals.
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What is a public key certificate
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It contains a public key and other information, is created by a certificate authority and is given to the participant with the matching private key
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How is an X.509 certificate revoked
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The owner of a public-key can issue a certificate revocation list that revokes one or more certificates
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What types of attacks are addressed by message authentication
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Masquerade, content modification, sequence modification, timing modification
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Why is it important to study the feistel cipher
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Most symmetric block encryption algorithms in current use
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Explain the avalance effect
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a property of any encryption algorithm such that a small change in either plaintext or key produces a significant change in the ciphertext
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What is the OSI security architecture
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a framework that provides a systematic way of defining the requirement for security and characterizing the approaches to satisfying those requirements.
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What are the three key security objectives as per OSI
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Confidentiality, integrity, availability
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List the categories of security services
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Authentication, access control, data confidentiality, data integrity
