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
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
3
Q
what is packet switching
A
a method of communicating packets of data across a network
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)
5
Q
what is in a packet header
A
- senders IP address
- recipients IP address
- protocol
- packet number
6
Q
what is in a packet trailer
A
- end of packet flag
- checksum
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
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
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
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
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
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
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
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
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
16
Q
what is malicious software (malware)
A
designed to cause inconvenience, loss or damage to programs, data or computer systems
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
40
Q
what is a DNS
A
- domain name server
- maps fully qualified domain names into IP addresses
- DNS stores a database of FQDNs and corresponding IP addresses
- organised into a heirarchy
- if one DNS server cannot resolve a lookup, the query will be passed to another
