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CompSci > Section 10 - The Internet > Flashcards

Section 10 - The Internet Flashcards

1
Q

What is a URL

A
  • Unifrom Resource Locator
  • specifies the location of a resource on the internet, inlcuding name and file type
  • hhtp = method
  • www = host
  • /webpage = location
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2
Q

what is an ip address

A
  • stands for internet protocol
  • unique address assigned to a network device
  • indicates where a packet of data is to be sent to or sent from
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3
Q

what is packet switching

A

a method of communicating packets of data across a network

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4
Q

what is a data packet

A
  • data that is to be transmitted across a network is broken down into more managabke chunks called packets
  • each packet contains a header, trailer and payload (the data)
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5
Q

what is in a packet header

A
  • senders IP address
  • recipients IP address
  • protocol
  • packet number
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6
Q

what is in a packet trailer

A
  • end of packet flag
  • checksum
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7
Q

what is a router

A
  • routers connect two networks together
  • determines which router to send to next
  • uses most efficient/shortest route
  • updates routing table to reflect network changes
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8
Q

what is a gateway

A
  • if a packet is being moved between networks with different protocols, then a gateway is required to translate
  • All of the header data is stripped from the packet and a new header is added in the format of the new network
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9
Q

what is a firewall

A
  • a firewall is either softwareor hardwae that controls access to and from a network
  • numbered doors called ports are opened so that only certain traffic is allowed to pass through
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10
Q

what is packet filtering

A
  • packets of data are inspected by the friewall to check which port they are attempting to access
  • if the IP address matched those recorded on the administrators permitted list, they are accepted and the port is opened
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11
Q

what is stateful inspection

A
  • the firewall maintains information about current connections
  • it can inspect the payload of packets
  • only allows relevant packets through
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12
Q

what is a proxy server

A
  • a proxy server makes a web request on behalf of your own computer, hiding the true request IP address from the recipient
  • proxy servers can be used for anonymous surfing and provides a cashe of previously visited sites to speed access
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13
Q

what is symmetric (private key) encryption

A
  • uses the same key to encrypt and decrypt data
  • this means the key must also be transferred to the same destination as the ciphertext
  • this causes security problems as the key can be intercepted as easily as the ciphertext to decrypt the data
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14
Q

what is asymmetric (public key) encryption

A
  • uses two separate, but related keys
  • the public key is made public and others wishing to send you data can use it for encryption, but not decryption
  • another private key is known only by you and is used for decryption
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15
Q

what is a digital signature

A
  • in order to verify the integrity of a message, the sender can add a digital signature to a message
  • the sender creates the signature by reducing the unencrypted message to produce a hash and encrypting the hash using their private key
  • the sender bundles the digital signature with the message and encrypts it using the recipients public key
  • recipient decrypts the bundle, uses the senders public key to decrypt the signature and compares the hash with their own calcuated hash
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16
Q

what is malicious software (malware)

A

designed to cause inconvenience, loss or damage to programs, data or computer systems

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17
Q

what is a virus/worm

A

a standalone program that does not require a user for it to spread or duplicate itself

18
Q

what is the TCP/IP stack

A
  • a set of rules used in turn to format a message so it can be sent over a network
  • contains four layers that each provide a specific function
  • stands for transmission control protocol/ internet protocol
19
Q

what are the four layers of TCIP/IP

A
  • application layer
  • transport layer
  • network layer
  • link layer
20
Q

what happens in the application layer

A
  • uses protocols related to the application being used
  • does not determine how the data is tranmistted, rather specifies the rules
21
Q

what happens in the transport layer

A
  • uses TCP to establish an end-to-end connection with the recipient computer
  • splits the data into packets, labels them with packet numbers and adds the port number based on http protocol
  • at the recieving end, this layer confirms all the packets have been recieved and requests any missing ones
  • performs error detection
22
Q

what happens in the network layer

A
  • uses the IP to address packets with the source and destination addresses
  • routers operate on this layer and forward each packet towards a socket (endpoint) formed of their IP address and port number
  • each router uses a routing table to insruct the next hop
23
Q

what happens in the link layer

A
  • adds the MAC adress identifying the NICs of the source and destination
24
Q

what happens when data is recieved

A
  • the link layer removes the MAC adrewss from each packet
  • the network layer removes the IP address from each packet
  • the transport layer remobes the port number from each packet and reassembles them in the correct order
  • the application layer presents the image data for the user in a browser
24
Q

what is a MAC adress

A
  • media access control address
  • unique 12 digit hexadecimal code that is hardcoded on every NIC during manufacture, uniquely identifying each physical device so data packets can be routed to them
25
Q

examples of well known ports

A
  • HHTP: 80 and 8080
  • HTTPS: 443
  • Post Office Protocols: 110
25
Q

how to improve code quality and protect from malware threats

A
  • guarding against buffer overflow attack
  • quarding aagainst SQL injection attack
  • use of strong passwords for login credentials
  • two factor authentification
25
Q

what is FTP

A
  • file transfer protocol is an application level protocol used to move files between computers on a network
  • ftp uses the client server model with seperate data and control channels
  • its a set of instructions that can communicate and exchange files
26
Q

what is secure shell

A
  • SSH is an encrypted protocol that allows secure communication between nodes across a network
  • ssh uses public key encryption to protect the data in communcication, requireing a digital ceritficate to authenticate the user
27
Q

what is the role of a mail server

A
  • mail servers are dedicated computers that route mail and store it until it can be recieved
  • it uses three protocols
28
Q

three protocols used by a mail server

A
  • SMTP: used to send emails and forward them between mail servers to their destination
  • POP3: retrieves emails from a mail server that stores incoming mail, then transferrs to the clients computer
  • IMAP: manages emails on a server to main synchronicity between devices
29
Q

what are the unusable ip addresses

A
  • 127.x.x.x are private, non-routable addresses used for LANs only
  • x.x.x.0 is the network identifyer
  • x.x.x.255 is the broadcast address on each network
  • x.x.x.1 is conventially the defualt router
30
Q

what are the parts of an ip address

A
  • network identifier: left handed bits of a 32 bit number, used to define the network where nodes are communicating
  • host identifier: right handed bits of a 32 bit number, used to identify the device
31
Q

what is classless adressing

A
  • the more hosts in each network, the fewer the networks that can be created
  • this system specifies the number of bits in the network ID
  • e.g. the network 210.54.101.0/24 has a network ID of 24 bits and a host ID of 8 bits
32
Q

what is subnetting

A
  • an organisation can chose to further subdivide the number of available hots IDs that they have between individual subnetworks
  • the subnet ID is formed from the host ID
  • this inproves security and can reduce data collisions
33
Q

what is a subnet mask

A
  • a subnet mask is used together with an ip addess to identify the network identifier within the address
  • a subnet mask is ANDed with the IP address to get the network identifier
34
Q

what is DHCP

A
  • dynamic host configuration protocol
  • automatically allocates IP addresses from a pool of available addresses to a host attempting to operate on a public network
  • means theres efficient allocation of addresses
  • allows hosts to move between networks
  • reduces the need for expert knowledge
35
Q

what is NAT

A

network address translation is used to convert IP addresses as they pass between a public address space (e.g. via a router) using a public IP address and a LAN with a private address space

36
Q

what is a well-known port

A

a port number that has a specific purpose

37
Q

what is a dns

A
  • domain name server
  • translates fully qualified domain names into IP addresses
  • DNS stores a database of FQDNs and corresponding IP addresses
  • organised into a heirarchy
38
Q

how can two computers connected to the internet have the same IP address

A
  • the computers have private, non-routable IP addresses
  • NAT is performed so the computers can communicate on the internet
39
Q

how can a firewall protect LANs

A
  • block/allow certain ports
  • packet filtering
  • stateful inspection
  • act as a proxy server
  • identify unusual behaviour from the host

CompSci (9 decks)

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