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GCSE OCR Computer Science > paper 1 - section 2 > Flashcards

paper 1 - section 2 Flashcards

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1
Q

what is a LAN?

A

A LAN (Local Area Network) is a network that covers a small geographical area, often located on a single sight.

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2
Q

who owns the hardware for a LAN?

A

the organization using it

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3
Q

Why use a LAN? (what are the positives?)

A
  • sharing files is easier - network users can access the same files, work collaboratively on them and copy files between machines
  • you can share the same hardware (like printers)
  • the internet connection can be shared between every device connected to the LAN
  • you can install and update software on all computers at once, rather than one-by-one
  • you can communicate with all LAN users cheaply and easily, e.g. with instant messaging
  • user accounts can be stored centrally, so users can log in from any device on the network
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4
Q

What is a WAN?

A

A WAN (Wide Area Network) is a network that connects LANs that are in different geographical locations. for example, a business with offices in three different countries would need a WAN for all their devices to connect together

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5
Q

Who owns the hardware for a WAN?

A

organisations hire infrastructure (e.g. communication lines) from telecommunications companies who own and manage the WAN. this is because a WAN is much more expensive to set up than a LAN.

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6
Q

Is the Internet a LAN or a WAN?

A

A WAN

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7
Q

Do most people have LANs or WANs in their homes?

A

Most people have LANs in their homes.

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8
Q

name 4 factors that can affect the performance of networks.

A

1 - Bandwidth (the amount of data that can be transferred in a given time)
2 - the amount of users (available bandwidth is shared between users of a network - too many users or heavy use may cause congestion and slow the network )
3 - mode of connection (wired connections are generally faster and more reliable than wireless)
4 - choice of hardware and network topology

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9
Q

What is a network interface controller (NIC)?

A

an internal piece of hardware that allows a device to connect to a network. they used to be on separate cards, but nowadays they’re built into the motherboard.

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10
Q

Do switches connect devices on a LAN or a WAN?

A

A LAN

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11
Q

Do switches transmit data in frames or packets?

A

frames

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12
Q

What address do switches use to transmit data?

A

a MAC address

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13
Q

Do routers transmit data within networks or between networks?

A

Between networks

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14
Q

Do routers direct data in frames or packets?

A

packets

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15
Q

Why are routers used in homes and offices?

A

to connect the LAN to the Internet

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16
Q

What are ethernet cables used for?

A

They are used to connect devices in a LAN

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17
Q

What are ‘twisted pair cables’?

A

pairs of wires that are twisted together to reduce interference.

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18
Q

Are ethernet cables twisted pair?

A

Yes

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19
Q

Are coaxial cables twisted pair?

A

No

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20
Q

Describe the structure of coaxial cables.

A

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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21
Q

How do fibre optic cables transmit data?

A

as light

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22
Q

list three advantages and one disadvantage of fibre optic cables.

A

Advantages:
They are high performance
They don’t suffer interference
They can transmit over very large distances without loss of signal quality

Disadvantage:
They very expensive

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23
Q

What does a wireless connection use to transmit data?

A

Radio Waves

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24
Q

What is a WAP?

A

A Wireless Access Point - you need one to connect to a wireless network, and it is basically a switch that allows devices to connect wirelessly.

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25
Q

Advantages of a Client-server network:

A
  • easier to keep track of files as they are stored centrally
  • easier to perform back-ups
  • easier to install and update software
  • easier to manage network security (e.g. anti-malware software and user access levels)
  • servers are very reliable and are always on
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26
Q

Disadvantages 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 all at once
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27
Q

Advantages of a peer-to-peer network:

A
  • easy to maintain - you don’t need any expertise or expensive hardware
  • no dependence on server - if one device fails the whole network isn’t lost
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28
Q

disadvantages of peer-to-peer networks:

A
  • no centralized management - devices need their updates and security installed individually. Backups are also more complicated
  • copying files between devices creates duplicate files, so it’s easy to lose track of what’s stored where and which files are up-to-date
  • peer machines are less reliable and data may be lost if one fails
  • machines are prone to slow down when other devices access them
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29
Q

describe a star network topology

A

all the devices are connected to a central switch or server that controls the network.

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30
Q

Pros of star topology:

A
  • if a device fails or a cable is disconnected, the rest of the network is unaffected.
  • it’s simple to add more devices to the network
  • better performance than other setups - data goes straight to the central service so all devices can transmit data at once and there a few data collisions
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31
Q

Cons of star topology:

A
  • in wired networks, every device needs a cable to connect to the central switch or server. This can be expensive, e.g. for an office building with 50 terminals
  • if there is a problem with the switch/server, the whole network is affected
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32
Q

Is a mesh network centralised or decentralised?

A

decentralised

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33
Q

describe a mesh network.

A

all networking devices are either directly or indirectly connected to each other without the need for one central switch or server. Mesh networks work by sending data along the fastest route from one device to another.

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34
Q

What is the main advantage of a mesh network?

A

there is no single point where the network can fail - if one device fails then the data is sent along a different route to get to its target

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35
Q

what is the traditional disadvantage of mesh networks, and why is it becoming less of a problem?

A

they can be very expensive - you need a lot of wires to connect so many devices together. However, now that more people are using wireless technology, mesh networks are a more practical option.

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36
Q

what is the difference between a full mesh topology and a partial mesh topology?

A

in a full mesh topology, every device is connected to every other device, whereas in a partial mesh topology, not all devices are directly connected.

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37
Q

what address does communication on the same network use?

A

a MAC address

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38
Q

why do we have MAC addresses?

A

every device needs a unique identifier so it can be found on a network

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39
Q

How are MAC addresses assigned to a device?

A

MAC addresses are assigned to all network enabled devices by the manufacturer. They are unique to the device

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40
Q

can MAC addresses by changed?

A

no

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41
Q

how many bits do MAC addresses have? (how long is their binary number)

A

MAC addresses are 48 or 64 bit binary numbers (i.e. a long string of 48 or 64 0s and 1s)

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42
Q

what decimal system are MAC addresses converted into to make them easier to use?

A

hexidecimal

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43
Q

what are MAC addresses mainly used by?

A

the Ethernet protocol on LANs. LAN switches read the MAC addresses and use them to direct data to the right device

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44
Q

what address is used for communication between different networks?

A

IP address

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45
Q

when are IP addresses used?

A

when sending data between TCP/IP networks e.g. over the internet

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46
Q

are IP addresses linked to hardware?

A

no

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47
Q

are MAC addresses linked to hardware?

A

yes

48
Q

when are IP addresses assigned?

A

they are assigned either manually (static) or automatically (dynamic) before the device can access the network

49
Q

what are static IP addresses?

A

permanent addresses

50
Q

what are static IP addresses used for?

A

they’re used to connect printers on a LAN and for hosting websites on the internet - companies don’t want the IP address of their website changing

51
Q

what are dynamic IP addresses and when are they assigned?

A

dynamic IP addresses are assigned when a device logs on to a network, meaning that it may have a different address every time it connects.

52
Q

which is more expensive - static IP addresses or dynamic IP addresses?

A

static IP addresses are more expensive - businesses pay big money for them. dynamic IP addresses are more cost-effective

53
Q

do Internet Service Providers (ISPs) commonly use dynamic or static IP addresses?

A

dynamic - they are more cost effective and can be reused

54
Q

how many bits is an IP address? (how many digits long is the binary number?)

A

either a 32-bit or a 128-bit binary number, depending on the version of IP you’re using

55
Q

what are 128-bit binary numbers translated into?

A

eight hexadecimal numbers

56
Q

what are 32-bit binary numbers converted into?

A

four denary (normal) numbers

57
Q

what is packet switching used for?

A

packet switching is used by routers to direct data packets on the internet and other IP networks

58
Q

what are the 6 steps of packet switching?

A
  1. 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
  2. each router reads the packet header and decides which way to send the packet next, according to the IP rules
  3. the way the data is sent next 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
  4. as the packets take different routes, they can arrive in the wrong order. The receiving device uses the packet numbers to reassemble them in the right order
  5. sometimes packets go missing in transit, so the receiving device checks periodically that all packets have been received. If it hasn’t received them within a certain time, it sends a timeout message back to the sending device
  6. if all the data is received and the checksums match, a receipt confirmation is sent to the sending devices
59
Q

why is packet switching an efficient use of the network?

A

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

60
Q

what protocol is the internet based around?

A

TCP/IP

61
Q

what is the world wide web?

A

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

62
Q

what are URLs?

A

addresses used to access web servers and resources on them

63
Q

what does a domain name server (DNS) do?

A

it translates a website’s domain name into it’s IP address - the internet has a network of domain name servers, meaning you don’t need to remember IP addresses to access websites - you can use domain names instead

64
Q

what is hosting?

A

when a business uses its servers to store files of another organisation

65
Q

what is the traditional use for hosting on the internet?

A

the hosting of website

66
Q

what is a relatively recent use of internet hosting?

A

general storage of user files and also providing online software

67
Q

what is the cloud?

A

general storage of user files and also providing online software - this is cloud computing, or simply ‘the cloud’. It acts like an extension of a traditional client-server network where user files are stored centrally on a network server

68
Q

what are 6 pros of the cloud?

A
  1. users can access files from any connected device
  2. easy to increase how much storage is available
  3. no need to buy expensive hardware to store data
  4. no need to pay IT staff to manage the hardware
  5. cloud host provides security and back ups for you
  6. cloud software will be updated automatically
69
Q

what are 5 cons of the cloud?

A
  1. need connection to the internet to access files
  2. dependent on host for security and back-ups
  3. data in the cloud can be vulnerable to hackers
  4. unclear who has ownership over cloud data
  5. subscription fees for using cloud storage and software may be expensive
70
Q

what are virtual networks?

A

networks that are entirely software-based

71
Q

how are virtual networks created?

A

by partitioning off some of a physical network’s bandwidth to form a separate network

72
Q

can more than one virtual network exist on the same physical network?

A

yes

73
Q

are virtual networks more or less efficient than standard physical networks?

A

more - they all share the same hardware

74
Q

does each virtual network have its own security? What does this mean?

A

yes, including its own firewall. this means virtual networks 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, or even know that it exists

75
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 offices on different sites, or to set up a school intranet that all the students can access from home

76
Q

what does a virtual LAN allow you to do?

A

split a LAN into several separate networks using the same hardware

77
Q

what is a passive attack?

A

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.

78
Q

are passive or active attacks harder to detect

A

passive attacks are harder to detect as the hacker is quietly listening

79
Q

what is the best defence against passive attacks?

A

data encryption

80
Q

what is an active attack?

A

when someone attacks a network with malware or other planned attacks

81
Q

what is the main defence against active attacks?

A

a firewall

82
Q

what is an insider attack?

A

Someone within an organisation exploits their network access to steal information

83
Q

what is a brute force attack?

A

a type of active attack used to gain information by cracking passwords through trial and error. Brute force attacks use automated software to produce hundreds of likely password combination, e.g. combining real words with predictable number sequences. Hackers may try lots of passwords against one username or vice versa.

84
Q

what helps to reduce the risk of a brute force attack?

A

simple measures like locking accounts after certain number of failed attempts and using strong passwords will reduce the risk of a brute force attack

85
Q

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

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

86
Q

what is malware?

A

malicious software that can harm devices

87
Q

what are 6 typical actions of malware?

A
  1. deleting or modifying files
  2. scareware - e.g. it tells the user their computer is infected with loads of viruses to scare them into following malicious links or paying for problems to be fixed
  3. locking files - 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
  4. spyware - secretly monitors user actions, e.g. key presses, and sends info to the hacker
  5. rootkits alter permissions, giving malware and hackers administrator-level access to devices
  6. opening backdoors - holes in someone’s security which can be used for future attacks
88
Q

what are three types of malware, and how can they access your device?

A
  1. viruses 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
  2. worms are like viruses but they self-replicate without any user help, meaning they can spread very quickly. they exploit weaknesses in network security.
  3. trojans are malware disguised as legitimate software. Unlike viruses and worms, trojans don’t replicate themselves - users install them not realising they have a hidden purpose
89
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

90
Q

describe a common form of social engineering that takes place over the telephone

A

someone rings up an employee of a company and pretends to be a network administrator or somebody else within the organisation. The social engineer gains the employee’s trust and persuades them to disclose confidential information - this might be personal (e.g. their login details) or sensitive company data

91
Q

is phishing social engineering or malware?

A

social engineering

92
Q

what is phishing?

A

phishing is when criminals send emails or texts to people claiming to be from a well-known business, e.g. a bank or an online retailer. The emails often contain links to spoof versions of the company’s website. They then request that the user update their personal information (e.g. password or bank account details). when the user inputs this data into the website they hand it all over to the criminals, who can then access their genuine account

93
Q

which networks are vulnerable to SQL injection attacks?

A

networks which make use of databases

94
Q

what is SQL?

A

Structured Query Language - it’s one of the main coding languages used to access information in databases

95
Q

what are SQL injections?

A

pieces of SQL typed into a website’s input box which then reveal sensitive informatio

96
Q

how do SQL injections work?

A

a website may allow you to view your account information, as long as you enter your password into an input box. If the website’s 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.

97
Q

what is a network policy?

A

a set of rules and procedures the organisation will follow to ensure their network is protected against attacks and unauthorised access

98
Q

what are 5 things a good network policy will do?

A
  1. regularly test the network to find and fix security weaknesses and investigate any problems
  2. use passwords to prevent unauthorised people from accessing the network
  3. enforce user access levels to limit the number of people with access to sensitive information
  4. install anti-malware and firewall software to prevent and destroy malicious software attacks
  5. encrypt sensitive data
99
Q

what is penetration testing?

A

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

100
Q

what is penetration testing used for?

A

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

101
Q

what are network forensics?

A

investigations undertaken to find the cause of attacks on a network.

102
Q

what must an organisation have in order to conduct network forensics?

A

a system of capturing data packets as they enter their network

103
Q

how do network forensics work?

A

an organisation captures all the data packets as they enter their network. after the network is attacked, these packets can be analysed to discover how the network was attacked and decide how to prevent further attacks

104
Q

what makes a strong password?

A

a strong password should be many characters long, use a combination of letters, numbers and symbols, and be changed regularly

105
Q

what do user access levels control?

A

which parts of the network different groups of users can access, e.g. business managers are likely to have a higher access level allowing them to access more sensitive data, like pay information

106
Q

how do user access levels help to make a network more secure?

A

user access levels help limit the number of people with access to important data, so help prevent insider attacks on the network

107
Q

what is anti-malware software designed to do?

A

to find and stop malware from damaging a network and the devices on it

108
Q

what do antivirus programs do?

A

isolate and destroy computer viruses

109
Q

what do companies use firewalls for?

A

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

110
Q

what is encryption?

A

Encryption is when data is translated into a code which only someone with the correct key can access, meaning unauthorised users cannot read it

111
Q

what is encrypted text called?

A

cipher text

112
Q

what is non-encrypted data called?

A

plain text

113
Q

what is encryption essential for?

A

sending data over a network securely

114
Q

what does the computer measure when it samples a sound wave?

A

amplitude and frequency

115
Q

what is metadata?

A

metadata means “data about data” and provides information about the data, e.g. file format, resolution, dimensions, colour depth, etc.

GCSE OCR Computer Science (15 decks)

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