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Computer Science > Section 2 - Networks > Flashcards

Section 2 - Networks Flashcards

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1
Q

how much area does a LAN cover?

A

it covers a small geographical area located on a single site

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2
Q

what is a LAN?

A

a local area network, owned by the organisation that uses it.
they can be wired (Ethernet cables) or wireless (Wi-Fi)

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3
Q

who owns LAN’s?

A

businesses, schools and universities

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4
Q

why do people use LAN’s?

A

sharing files is easier - network users can access the same files, work collaboratively on them and copy between machines
hardware can be shared
internet connection can be shared
you can install and update software on all computers at once
you can communicate with LAN users cheaply and easily
user accounts can be stored centrally, so users can log in from any device on the network

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5
Q

what is a WAN?

A

wide area network.
it connects LAN’s that are in different geographical locations. e.g. a WAN can connect offices in different countries.
the internet is 1 big WAN

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6
Q

do people buy WAN’s?

A

organisations hire infrastructure from telecommunications companies, who own and manage the WAN. WAN’s are more expensive to set up than LAN’s

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7
Q

how are WAN’s connected?

A

using fibre or copper telephone lines, satellite links or radio links

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8
Q

what is bandwidth?

A

the amount of data that can be transferred in a given time. the greater the bandwidth, the better the network can perform

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9
Q

how can a network become congested?

A

available bandwidth is shared between users of a network - too many users or heavy use may cause congestion and slow the network. you can limit bandwidth available to individual users to solve this

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10
Q

are wired or wireless connections faster?

A

wired connections are generally faster and more reliable than wireless. fibre optic cables give better performance than copper cables.

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11
Q

what does wireless performance depend on?

A

signal quality, this means it is affected by the range of the device, the amount of interference from other devices and physical obstructions like thick walls in buildings. choice of hardware and network topology also have a big effect

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12
Q

what is a network interface controller?

A

an internal piece of hardware that allows a device to connect to a network. these used to be on separate cards, but now they’re built into the motherboard. they exist for both wired and wireless connections

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13
Q

what do switches do?

A

they connect devices on a LAN. they receive data (in units called frames) from 1 device and transmit this data to the device on the network with the correct MAC address

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14
Q

what do routers do?

A

they are responsible for transmitting data between networks - they’re always connected to at least 2 different networks
they direct data (in packets) to their destination.
they are used in homes and offices to connect the LAN to the internet

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15
Q

what are Ethernet cables used for?

A

to connect devices in a LAN. most common are CAT 5e and CAT 6. they are ‘twisted pair’ cables, containing 4 pairs of copper wires which are twisted together to reduce internal interference

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16
Q

what are coaxial cables?

A

they are made of a single copper wire surrounded by a plastic layer for insulation and a metallic mesh which provides shielding from outside interference

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17
Q

what are fibre optic cables?

A

they transmit data as light. they are high performance cables that don’t suffer interference and can transmit over very large distances without loss of signal quality

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18
Q

what devices use radio waves to transmit data?

A

mobile phones, TV’s and wireless networks

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19
Q

what is needed to set up a wireless network?

A

a WAP (wireless access point) device.

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20
Q

what are WAP’s?

A

its basically a switch that allows devices to connect wirelessly. they are not hotspots, which are locations where you can connect to a WAP

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21
Q

how can devices have wireless capability?

A

many modern devices have the necessary hardware built in, but devices that don’t can often use a dongle

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22
Q

what are USB dongles?

A

they can be plugged into computers to allow them to connect wirelessly to the internet

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23
Q

what are HDMI dongles?

A

they can use wireless networks to stream high-quality video to a TV

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24
Q

what 2 radio frequencies bands does WI-FI use?

A

2.4 GHz and 5 GHz

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25
Q

why are only certain channels used in the 2.4 GHz frequency band?

A

the bands are split into numbered channels that each cover a small frequency range. the channels overlap and WiFi performance is affected by interference between networks. to avoid this only certain channels that are spaced apart should be used

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26
Q

what are the advantages of the 2.4 GHz frequency band?

A

has a greater range, so can serve devices across a wider area
better at getting through solid objects/ walls

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27
Q

what are the advantages of the 5 GHz frequency band?

A

much faster when communicating over a short distance

there are more non-overlapping channels, so there’s less chance of interference from other devices

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28
Q

how does the client-server network work?

A

files and software are stored centrally.

clients send requests to the server e.g. asking for data. the server processes the request and responds

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29
Q

in a client server network what does the server do?

A

stores user profiles, passwords and access information - it may request a password before fulfilling certain requests or deny requests to users without the right access information

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30
Q

what are the pros of a client-server network?

A

easier to keep track of files as he’re stored centrally
easier to perform back-ups
easier to install and update software
easier to manage network security
servers are very reliable and are always on

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31
Q

what are the cons of a client-server network?

A

expensive to set up and needs IT specialists to maintain the network and server
server dependence - if the server goes down all clients lose access to their work
the server may become overloaded if too many clients are accessing it at once

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32
Q

how do peer-to-peer networks work?

A

all devices are equal, connecting directly to each other without a server.
files are stored on individual devices and share them with others
they can be used at home to share files between devices, or connect devices to a printer

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33
Q

what are the pros of peer-to peer?

A

easy to maintain - you don’t need any expertise or expensive hardware
no dependence on server - if 1 device fails the network is unaffected

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34
Q

what are the cons of peer-to peer?

A

no centralised management - devices need their updates and security installed individually. backups are also more complicated
copying files between devices creates duplicate files - its easy to lose track of whats stored where and which files are up-to-date
peer machines are less reliable and data may be lost if 1 fails
machines are prone to slow down when other devices access them

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35
Q

what is a star topology?

A

all devices are connected o a central switch or server that controls the network.
the central switch allows many devices to access the server simultaneously
they can be wired and wireless

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36
Q

what are the pros of a star topology?

A

if a device fails or a cable is disconnected, the rest of the network is unaffected
its simple to add more devices to the network
better performance than other setups - data goes straight to the central device so all devices can transmit data at once and there are fewer data collisions

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37
Q

what are the cons of a star topology?

A

in wired networks, every device needs a cable to connect to the central switch or server. this can be expensive
if there is a problem with the switch/server, the whole network is affected

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38
Q

what is a mesh topology?

A

it is decentralised - networking devices are either directly or indirectly connected to every other 1 without the need for a central switch or server. they send data along the fastest route from 1 device to another

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39
Q

what are the advantages of mesh topology’s?

A

there is no single point where the network can fail, if 1 device fails data can be sent along an alternative route

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40
Q

what are the disadvantages of mesh topology’s?

A

if it is a wired network it is very expensive, but with wireless technology, they are more practical

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41
Q

what is a full mesh?

A

where every device is connected to every other device

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42
Q

what is a partial mesh topology?

A

not all devices are fully-connected

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43
Q

what is a protocol?

A

a set of rules for how devices communicate and how data is transmitted across a network

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44
Q

what do protocols cover?

A

how communication between 2 devices should start and end, how data should be organised, and what devices should do if data goes missing

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45
Q

what are MAC addresses?

A

unique addresses assigned to all network-enabled devices by the manufacturer. they can’t be changed.

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46
Q

how long are MAC addresses?

A

48 or 64-bit binary numbers, that are converted to hexadecimal

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47
Q

how are MAC addresses used?

A

they are mainly used by the Ethernet protocol on LAN’s. LAN switches read the MAC addresses and use them to direct data to the right device

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48
Q

when are IP addresses used?

A

when sending data between TCP/IP networks e.g. over the internet.
they aren’t linked to hardware, they are assigned either manually or automatically before the device can access the network

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49
Q

what are static IP addresses?

A

permanent addresses. they’re used to connect printers on a LAN, and for hosting websites on the internet - companies don’t want their IP address changing, they can be expensive and businesses pay lots of money for them.

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50
Q

what are dynamic IP addresses?

A

they are assigned when a device logs onto a network, so it may have a different address every time it connects. internet device providers (ISPs) usually use them because they are more cost effective and can be reused

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51
Q

how long are IP addresses?

A

they can be 32 bit or 128 bit binary numbers, depending on the version of IP. longer 128 bit numbers are translated into 8 hexadecimal numbers. the 32 bit ones are converted into 4 denary numbers

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52
Q

what do data packets have?

A

a header
a payload
a checksum

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53
Q

what is in a packets header?

A

the control information. the control information includes the packet’s destination, the source address and the packet number

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54
Q

what is the packets payload?

A

the thing a person is likely to read, and the whole reason the data packet has been sent in in the 1st place. it might be part of an email, document, web page or streamed video

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55
Q

what is the checksum of a packet?

A

it is a form of validation used to check that the payload data hasn’t been corrupted during transit. the sending and receiving devices both calculate a checksum by performing a function on the payload. if the values match the data has been received correctly

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56
Q

how is lots of data able to be sent across the internet?

A

the sending device splits the data into packets to be sent across the network. each packet is given a packet number to show the order of the data

57
Q

how is packet switching used by routers?

A

each router reads the packet header and decides which way to send the packet, according to the IP rules
the way the data is sent changes depending on network traffic so the packets can take different routes. if a router receives too many packets at once, it may prioritise some over others

58
Q

why do data packets need packet numbers?

A

the packets take different routes, so they can arrive in the wrong order. the receiving device uses the packet numbers to reassemble them in the right order

59
Q

when is a timeout message sent?

A

the receiving device checks periodically that all the packets have been received, if they haven’t arrived in a certain time then a timeout message is sent. this is done because sometimes packets go missing

60
Q

what happens if all the data is received, and the checksums match?

A

a receipt confirmation is sent to the sending device

61
Q

why is packet switching an efficient use of the network?

A

because there are so many possible routes that data can take - packets can reach their receiving device even if there’s heavy traffic

62
Q

what is TCP/IP?

A

a protocol that dictates how data is sent between networks. its made up of 2 protocols : TCP and IP

63
Q

what does the transmission control protocol do?

A

it sets the rules for how devices connect on the network. its in charge of splitting the data into packets and reassembling the packets back into the original data. it also checks the data is correctly sent and delivered

64
Q

what does internet protocol do?

A

its responsible for packet switching

65
Q

what is HTTP?

A

hyper text transfer protocol. its used by web browsers to access websites and communicate with web servers

66
Q

what is HTTPS?

A

HTTP secure, its a more secure version of HTTP. it encrypts all information sent and recieved

67
Q

what is FTP

A

file transfer protocol. used to access, edit and move files between devices on a network, e,g, to access files on a server from a client computer

68
Q

what is POP3?

A

post office protocol, version 3. its used to retrieve emails from a server. the server holds the email until you download it, at which point it is deleted from the server

69
Q

what is IMAP?

A

internet message access protocol. its used to retrieve emails from a server. the server holds the email until you delete it - you only download a copy. most web-based email recipients use it

70
Q

what is SMTP?

A

simple mail transfer protocol. its used to send emails. also used to transfer emails between servers

71
Q

what is a layer?

A

a group of protocols which have similar functions. the are self-contained so protocols in each layer can do their job without needing to know whats happening in other layers. each layer serves the layer above it

72
Q

what are the 4 different layers?

A

layer 4 - application layer
layer 3 - transport layer
layer 2 - network layer
layer 1 - link layer

73
Q

what does the application layer do?

A

it turns data into websites and other applications and vice versa. e.g. HTTP, FTP, SMTP

74
Q

what does the transport layer do?

A

controls data flow - e.g. splitting data into packets and checking packets are correctly sent and delivered. e.g. TCP

75
Q

what does the network layer do?

A

make connections between networks, directly data packets and handling traffic. used by routers. e.g. IP

76
Q

what does the data link layer?

A

it passes data over the physical network. its responsible for how bits are sent as electrical signals over cables, wireless and other hardware. e.g. ethernet

77
Q

what are the advantages of using layers?

A

it breaks network communication into manageable pieces
they are self contained
each layer has set rules

78
Q

how is breaking network communication into manageable pieces an advantage of layers?

A

it helps developers concentrate on only 1 area of the network without having to worry about the others

79
Q

how is being self contained an advantage of layers?

A

they can be changed without the other layers being affected

80
Q

how is each layer having set rules an advantage of layers?

A

it forces companies to make compatible, universal hardware and software, so different brands will work with each other and always work in basically the same way

81
Q

what is the internet?

A

its a WAN which connects devices and networks

82
Q

what is the world wide web?

A

a collection of websites that are hosted on web servers and accessed through the http protocol

83
Q

what are URLs?

A

addresses used to access web servers and resources on them. they are made of a protocol, domain name and path

84
Q

what does a domain name server do?

A

it translates a websites domain name into its IP address. the internet has a network of domain name servers, meaning you don’t need to remember IP addresses to access websites

85
Q

what is hosting?

A

when a business uses its servers to store files of another organisation. the traditional use for this on the internet is the hosting of websites

86
Q

what is internet hosting used for?

A

general storage of user files and providing online software - this is cloud computing (the cloud). it acts like an extension of a traditional client-server network where user files are stored centrally on a network server

87
Q

what are the pros of the cloud?

A

users can access files from any connected device
easy to increase how much storage is available
no need to buy expensive hardware to store data
no need to pay IT staff to manage the hardware
cloud host provides security and back ups for you
cloud software will be updated automatically

88
Q

what are the cons of the cloud?

A

need connection to the internet to access files
dependent on host for security and back-ups
data in the cloud can be vulnerable to hackers
unclear who has ownership over cloud data
subscription fees for using cloud storage and software may be expensive

89
Q

what is a virtual network?

A

a network that is entirely software-based. virtual networks are created by partitioning off some of a physical network’s bandwidth to form a separate network

90
Q

how many virtual networks can exist on a physical network?

A

several virtual networks can exist on the same physical network. these networks all share the same hardware, making virtual networks more efficient than standard physical networks.

91
Q

why can virtual networks only be accessed with certain software?

A

each virtual network has its own security, including firewall. this means they can only be accessed by using certain software or login information - other people could be using the same physical network and not have access to the virtual network

92
Q

what is a virtual private network (VPN)?

A

a type of virtual network that can be used to send data securely over a large network, like a WAN or the internet e.g. a VPN can be used to send data securely between 2 offices on different sites, or to set up a school intranet that all the students can access from home

93
Q

what is a virtual LAN?

A

it allows you to split a LAN into several separate networks using the same hardware

94
Q

what is a passive attack?

A

where someone monitors data travelling on a network and intercepts any sensitive information they find. they use network-monitoring hardware and software such as packet sniffers. they are hard to detect because packet sniffers don’t actively do any harm

95
Q

what is the best defence against passive attacks?

A

data encryption

96
Q

what are active attacks?

A

when someone attacks a network with malware or other planned attacks. they are more easily detected

97
Q

what is the best defence against active attacks?

A

firewall

98
Q

what is an insider attack?

A

someone within an organisation exploits their network access to steal information

99
Q

what is a brute force attack?

A

a type of active attack used to gain information by cracking passwords through trial and error. they use automated software to produce hundreds of likely password combinations

100
Q

how do brute force attacks work?

A

they may try lots of passwords against 1 username or vice versa

101
Q

how can risk of brute force attacks be reduced?

A

simple measures like locking accounts after a certain number of failed attempts and using strong passwords

102
Q

what is a denial-of-service attack (DoS)?

A

where a hacker tries to stop users from accessing a part of a network or website. most DoS attacks involve flooding the network with useless traffic, making the network extremely slow or completely inaccessible

103
Q

what are some typical actions of malware?

A 
deleting or modifying files
scareware
locking files
spyware
rootkits
opening backdoors
104
Q

what is an example of scareware?

A

it tells the users their computer is infected with loads of viruses to scare them into following malicious links or paying for problems to be fixed

105
Q

how can malware be used to lock files?

A

ransomware encrypts all the files on a computer. the user receives a message demanding a large sum of money be paid in exchange for a decryption key

106
Q

what is spyware?

A

it secretly monitors user actions, e.g. key presses, and sends info to the hacker

107
Q

what are rootkits?

A

they altar permissions, giving malware and hackers administrator-level access to devices

108
Q

what a re ‘backdoors’?

A

holes in someones security which can be used for future attacks

109
Q

what different ways can malware access your device?

A

viruses
worms
Trojan horses

110
Q

what do viruses do?

A

attach (by copying themselves) to certain files, e.g. .exe files and autorun scripts. users spread them by copying infected files and activate them by opening infected files

111
Q

what do worms do?

A

they are like viruses but they self-replicate without any user help, meaning they can spread very quickly. they exploit weaknesses in network security

112
Q

what are Trojan horses?

A

malware disguised as legitimate software. they don’t replicate themselves - users install them not realising they have a hidden purpose

113
Q

what is social engineering?

A

a way of gaining sensitive information or illegal access to networks by influencing people, usually the employees of large companies

114
Q

what is a common form of social engineering?

A

it takes place over the telephone - someone rings an employee and pretends to be a network administrator or someone within the organisation. they gain the employees trust and persuade them to disclose confidential information, this might be personal or sensitive company details

115
Q

what is phishing?

A

when criminals send emails or texts to people claiming to be from a well-known business. the emails often contain links to spoof versions of the company’s website.

116
Q

how do criminals use phishing?

A

they can request that the user update their personal information. when the user inputs this data into the website they give to the criminals, who can access their genuine accounts

117
Q

how many emails do phishers send?

A

they often send it to thousands of people, in the hope that someone will read the email and believe its contents to be legitimate

118
Q

how can phishing be protected against?

A

many email programs, browsers and firewalls have anti-phishing features that will reduce the number of phishing emails to received. some giveaways are poor grammar.

119
Q

what does SQL stand for?

A

structured query language

120
Q

what is SQL?

A

1 of the main coding languages used to access information in databases

121
Q

what are SQL injections?

A

pieces of SQL typed into a websites input box which then reveal sensitive information

122
Q

how could an SQL injection be used?

A

if the websites SQL code does not have strong enough input validation, then someone may be able to enter a piece of SQL code which allows them to access other people’s account information as well as their own

123
Q

what does a good network policy do?

A 
regularly test the network 
use passwords 
enforce user access levels
install anti-malware and firewall software 
encrypt sensitive data
124
Q

why should a good network policy regularly test the network?

A

to find and fix security weakness and investigate any problems

125
Q

why should a good network policy use passwords?

A

to prevent unauthorised people from accessing the network

126
Q

why should a good network policy enforce user access levels?

A

to limit the number of people with access to sensitive information

127
Q

why should a good network policy install anti-malware and firewall?

A

to prevent and destroy malicious software attacks

128
Q

what is penetration testing?

A

pentesting is when organisations employ specialists to simulate potential attacks on their network

129
Q

why is pentesting used?

A

to identify possible weakness in a network’s security by trying to exploit them. the results of the pentest are then reported back

130
Q

what are network forensics?

A

investigations undertaken to find the cause of attacks on a network. to conduct network forensics, an organisation needs to have a system of capturing data packets as they enter their network

131
Q

what happens in network forensics after the network is attacked?

A

the captured data packets can be analysed to discover how the network was attacked and decide how to prevent future attacks

132
Q

how can unauthorised users be prevented from accessing the network?

A

passwords. they should be strong - they should be many characters long , use a combination of letters, numbers and symbols - and be changed regularly

133
Q

what do user access levels do?

A

control which parts of the network different groups of users can access

134
Q

example of user access level:

A

business managers are likely to have a higher access level so they can access more sensitive data, like pay information. they may also have write access to files that others can only read and the ability to change employees’ access levels

135
Q

what is anti-malware software?

A

its designed to find and stop malware from damaging a network and the devices on it. there are lots of different types, including antivirus programs which isolate and destroy computer viruses

136
Q

how do companies use anti-malware?

A

companies use firewalls to block unauthorised access. firewalls examine all data entering and leaving the network and block any potential threats

137
Q

what is encryption?

A

when data is translated into a code which only someone with the correct key can access, meaning unauthorised users can’t read it. it is essential for sending data over a network securely

138
Q

what is encryption text called?

A

cipher text, non- encrypted data is called plain text

Computer Science (12 decks)

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