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Computer Science JA > 1.3 - Exchanging data > Flashcards

1.3 - Exchanging data Flashcards

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1
Q

What is a standalone machine?

A

A single computer not connected to anything else.

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2
Q

What is a network?

A

2 or more devices connected to each other.
(Either by cable or wireless)

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3
Q

What are the 5 advantages of networks?

A
  • Users can share files.
  • Users can share peripherals and connections to other networks such as the internet.
  • Users can access files from any computer on the internet.
  • Servers can control security, software updates and the backup of data.
  • Communication with other people. (e.g. email + social networking)
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4
Q

What are the 4 disadvantages of networks?

A
  • Increased security risks to data.
  • Malware and viruses easily spreadable between computers.
  • Computers connected may not work if server fails.
  • Computers may run slower if there is alot of data travelling on the network.
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5
Q

What are standards?

A

Set of hardware & software specifications that allow manufactures to create products and services that are compatible with each other.

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6
Q

How do standards need to be used for characters sets?

A

If 1 device recognises 01000001 as A, other devices also need to recognise it as A.

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7
Q

What is an example of a standard?

A

HTML - adopted within the WWW to be the standard for display of web pages in browsers.

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8
Q

What is a protocol?

A

It is a set of rules that ensure devices follow the same standards

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9
Q

What is TCP?

A

Transmission Control Protocol

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10
Q

What does TCP do?

A
  • Communication over LAN/WAN.
  • Provides and Error free transmission between two routers.
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11
Q

What is IP?

A

Internet Protocol

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12
Q

What does IP do?

A
  • Communication over LAN/WAN.
  • Routes packets across a wide area network.
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13
Q

What is UDP?

A

User Datagram Protocol

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14
Q

What are the 3 characteristics of UDP?

A
  • Alternative to TCP but has no error checking + is less relaible so mainly obsolete.
  • Sends short messages using datagrams (speed is more important than accuracy).
  • Maintains an open two way connection ideal for gaming.
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15
Q

What is HTTP?

A

Hypertext Transfer Protocol

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16
Q

What does HTTP do?

A
  • Way for client & server to send and receive requests and deliver HTML web pages.
  • Fundamental protocol of the WWW (World wide web).
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17
Q

What is HTTPS?

A

Hypertext Transfer Protocol Secure

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18
Q

What does HTTPS do?

A
  • Way for client & server to send and reciebe requests and deliver HTML web pages.
  • Fundamental protocol of the WWW (World wide web).
  • Adds encryption and authentication. (Should be used when a website deals with sensitive information).
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19
Q

What is FTP?

A

File transfer protocol

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20
Q

What does FTP do?

A
  • Sends files between computers, normally on a WAN.
  • People often use FTP clients.
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21
Q

What is POP?

A

Post Office Protocol

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22
Q

What does POP do?

A

Retrieves emails form a mail server and transfers them to your device, removing them from the server in the process.

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23
Q

What is IMAP?

A

Internet Message Access Protocol

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24
Q

What does IMAP do?

A

Keeps emails on the mail server, maintaining synchronicity between devices.

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25
Q

What is SMTP?

A

Simple Mail Transfer protocol

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26
Q

What does SMTP do?

A

Transfers outgoing emails between servers and from clients to servers

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27
Q

What is TCP/IP?

A

Transmission Control Protocol/Internet Protocol Stack.
It is the foundation of communication accross the internet

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28
Q

What are FTP clients.

A

Software applications that sit on top of the actual FTP protocol.
When interacting with the program, the client generates + sens the appropriate FTP commands.

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29
Q

What is the internet?

A
  • A WAN.
  • A collection of interconnected networks, routers, cables, sattelites, and other hardware spanning the world.
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30
Q

How is a home network connected through a wireless router?

A
  • The router is connected to an ISP (typically via a telephonr connection or a fibre optic cable).
  • ISP is connected to the DNS and other routers making up the backbone of the internet.
  • Routers also connected to devices on their own LANS, other routers on WANS, Servers.
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31
Q

What is an ISP?

A

Internet Service Provider.

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32
Q

What is a DNS?

A

Domain Name Service.

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33
Q

What is the concept of layering?

A
  • Divides the complex task of networking into smaller, simple tasks that work in tandem with each other.
  • The hardware/software of each layer has a defined responsibility and each one provides a service to the layer above it.
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34
Q

What are the 3 advantages of layering?

A
  • Reducing complex problems into smallersub-problems.
  • Devices can be manufactured to operate at a particular layer.
  • Products from different vendors will work together.
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35
Q

What are the 4 layers of the TCP/IP stack?

A

Application -> Transport -> Internet -> Data link.

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36
Q

What happens during the application layer?

TCP/IP stack

A

Network applicatons such as web browsers or email applications operate at this layer. So an appropriate protocal is chosen; e.g. FTP, HTTP, HTTPS, SMTP, IMAP

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37
Q

What happens during the application layer?

TCP/IP stack

A

Network applicatons such as web browsers or email applications operate at this layer.
Protocols = FTP, HTTP, HTTPS, SMTP, IMAP

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38
Q

What happens during the transport layer?

TCP/IP stack

A

Establishes an end-to-end connection and maintaining conversations between application processors and they agree settings such as language + packet size.
Protocols use port numbers to track sessions and this info is added to the header.
- Once connection is made, data is split into packets and these are added to each packets;
- Its number/sequence, the total no. of packets, the port number that the packet should use.
Protocols = TCP, UDP.

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39
Q

What happens during the internet layer?

TCP/IP stack

A
  • The source IP address and destination IP address are added to each packet.
  • All routers operate at this layer. They use the IP address to find out where is is going, from the socket.
  • Protocols = IP.
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40
Q

What happens during the link layer?

TCP/IP stack

A
  • The physical connection between network devices.
  • It adds the MAC address of source device and destination device.
  • When transmitting data between routers over a WAN, the MAC address is changed at each hop on the route.
    Medium = Copper twisted pair, fibre, Wi-fi.
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41
Q

What is a socket?

A

IP address + port.
e.g. 127.56.87.2:80.

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42
Q

What is a MAC address?

A

Media Access Control address

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43
Q

What address is needed for communication on a LAN?

A

Communication between 2 devices on the same LAN, only requires the link layer - which creates a frame using MAC addresses (unique to each device).

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44
Q

What addresses are needed for communication on a WAN?

A

Communication between 2 devices on different networks (WAN) requires both the network layer (Uses the IP address to create a packet) and the link layer frame. (Mac Address)

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45
Q

What does the MAC address tell you?

A

Who you are.

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46
Q

What does the IP address tell you?

A

Where you are.

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47
Q

How is the MAC address stored?

A

Switches store the address for connected LAN devices only.

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48
Q

How is the IP address stored.

A

Routers cache some IP addresses.

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49
Q

How are the MAC address and IP address used in tandem to find a device?

A
  • MAC address can’t find device on WAN (Too large an area with too many devices).
  • IP address tells us roughly where to go even if we don’t know the specific device the message is for.
  • Both needed to route traffic over a WAN, e.g. the internet.
50
Q

What is LAN switching (the ARP protocl)?

A
  • Use the ARP protocol for the host to broadcast and find the destination MAC address (If it doesn’t know it).
  • As traffic goes through the switch, switch examines source and destination MAC addresses and learns which applies to which device.
  • Eliminates need for broadcasting in the future.
51
Q

What are modern routers?

A

They are both routers and switches capable of performing both LAN switching and WAN routing.

52
Q

What are the 6 features of WAN routing?

A
  • Done if hosts are on different networks and data is transmitted via a router.
  • Destination MAC address will be address of the router.
  • When frame reaches the router, the router works out where it needs to send the packet by the destination IP in the header.
  • Router sets its own MAC address as the source and next device as the destination.
  • Router can also use the ARP protocol to find the destination MAC address if the router doesn’t know it.
  • (If several routes to the destination, the MAC address will be overwritten each hop).
53
Q

How does the TCP/IP protocol utilise layers?

A
  • Original message split and wrapped up in segments.
  • Segments are wrapped up in packets which are then wrapped up in frames.
  • Once frames reach final destination, they travel up through the layers of the TCP/IP protocol in reverse order (stripping off the headers & tails as they go).
  • Then the destination application recieves the message.
54
Q

What is the World Wide Web?

A

Collection of files with information stored in hypertext (Web pages) and other files, hosted on web servers.

55
Q

What do web servers host?

A

Store the files and handle client requests. e.g. a HTTP GET request for a page/resource.
Web page (Stored as text; HTML, CSS, JavaScript) is sent to web browser application which uses rules to render it correctly.

56
Q

What are the 5 steps to opening a URL in a browser?

A
  1. User request URL via a browser.
  2. The broswer sends the name to a Domain Name System (DNS).
  3. The DNS maps the domain name to an IP address and returns it to the browser.
  4. A GET request for the web page or resource is sent to the web server using the IP address.
  5. The requested web page or resource is returned to the client’s web browser.
57
Q

What are the 8 stages of the Domain Name System (DNS)?

A
  1. Human readable URL is recieved by DNS resolver server server.
  2. The server then queries a DNS root name server.
  3. The root server responds with the address of the top-level domain server (TLD) for .com.
  4. The resolver makes a request to the .com TLD server.
  5. The TLD server then responds with the IP address of the domain’s name server, google.com.
  6. The recursive resolver sends a query to the dopmain’s name server.
  7. The Ip address of goole.com (8.8.8.8) is then returned to the resolver from the name server.
  8. Finally, the DNS resolver responds to the web browser with the IP address google.com.
58
Q

What is a LAN?

A
  • A local area network (LAN) is a network that covers a small geographical area. (typically located on a single site).
  • All hardware tends to be owned and controlled by the organisation using it.
59
Q

What 3 things do LANs typically use to connect?

A
  • UTP cable.
  • Fibre optic.
  • Wi-Fi.
60
Q

What is a WAN?

A
  • A wide are network (WAN) is a network covering a large geographical area. Multiple LANs physically located in different areas are connected to form a WAN.
  • The infastructure connecting LANs to make a WAN is leased from telecommunication companies who own and manage it.
61
Q

What 3 things are WANs typically connected by?

A
  • Telephone lines.
  • Fibre optic cables.
  • Satellite links.
62
Q

How does circuit switching work?

A
  • Creates a temporary and dedicated link of fixed bandwidth between the source and destination that only lasts until the transmission is complete.
  • Provides the basis for traditional telephone networks.
63
Q

What are the guarentees of circuit switching?

A
  • Quality of the transmission through dedicated bandwidth; excellent for data that needs a constant link end-to-end, e.g. real-time video.
64
Q

What is the downside to circuit switching?

A
  • Potential bandwidth can be wasted.
65
Q

How does packet switching work?

A
  • Breaks streams of data into smaller blocks, each sent independently of one another.
  • At each node, packets are sent via whichever route the node decides is the least congested; maximising bandwidth but doesn’t guarentee the quality of the transmission.
  • packets may take different routes to their destination and arrive out of order.
66
Q

What are the 2 advantages to packet switching?

A
  • More affordable & efficient than circuit switching as all bandwidth can be used at once.
  • Requires less complex infastructure and can easily respond if parts of the network fail.
67
Q

What are the 5 characteristics of Circuit switching?

A
  • Physical path between source and destination.
  • All packets use the same path.
  • Reserves bandwidth in advance.
  • Can cause a lot of bandwidth wastage.
  • No store and forward transmission.
68
Q

What are the 5 characteristics of Packet switching?

A
  • No physical path.
  • Packets travel independently.
  • Does not reserve bandwidth.
  • No bandwidth wastage.
  • Supports store and forward transmission.
69
Q

What are the 3 aims of network security?

A
  • Only allow authorised users to access what they need.
  • Prevent unauthorised access.
  • Minimise the potential damage caused by unauthorised access.
70
Q

What is a hacker?

A

A person who attemps to gain access to a computer system with intent of damaging data or somehow harming that system.

71
Q

What is a Black-hat hacker?

A

They attempt to gain access via nefarious means, typically to steal company secrets or cause damage.

72
Q

What is a White-hat hacker?

A
  • Security experts (often ex-hackers) employed by a company.
  • Also called ethical hackers, they use their expertise to try and find vulnerabilities and fix them.
73
Q

What is a Grey-hat hacker?

A
  • They aren’t employed by a company but still attempt to locate flaws in company-wide computer systems as a hobby.
  • Technically illegal but they inform the company of the flaw so it can be fixed.
74
Q

What is malware?

A

Umbrella term for any computer code written with the intent to frustrate or harm.

75
Q

What 4 typical effects of malware?

A
  • Deleting, corrupting or encrypting files.
  • Causing computers to crash, reboot or slow down.
  • Reducing network speeds.
  • Logging keyboard inputs and sending them to hackers.
76
Q

What is a Virus?

A

A piece of code capable of copying itself and spreading throughout a system.
Typically designed to have a detrimental effect like corrupting a file system or destroying data.

77
Q

What is Spyware?

A
  • It covertly obtains information about the user’s computer activities by transmitting data from their devices. Harvesting sensitive and personal data.
78
Q

What are the 8 pieces of data can spyware access?

A
  • Internet surfing habits.
  • Email addresses.
  • Visited web pages.
  • Downloads/download habits.
  • Passwords.
  • Credit card numbers.
  • Keystrokes.
  • Cookies.
79
Q

What is a Denial-of-service (DoS) attack?

A
  • Attaker floods a server with useless traffic, causing the server to become overloaded.
  • Doesn’t typically result in theft or loss of data/other assets but can cost a great deal of time and money to handle.
80
Q

Who do DoS attacks often attack?

A
  • Often target web servers of high-profile organisations. E.g. banks, large-scale e-commerce businesses & the government.
  • Many past attacks exploited the limitations of the TCP/IP stack.
81
Q

What is a distributed denial-of-service (DDoS) attack?

A
  • When multiple systems orchestrate a synchronised DoS attack against a single target.
82
Q

How does a distributed denial-of-service (DDoS) attack happen?

A
  • The target is attacked from many locations at once.
  • E.g. several devices unknowingly became infected and now act as zombies carrying out independent DoS attacks. (Often without device owner’s knowledge).
83
Q

What is a SQL injection?

A
  • A code injection technique used to attack data-driven applications.
  • Designed to exploit vulnerabilities in poorly coded database applications.
84
Q

How is a SQL injection executed?

A

Code in entered into input text boxes and is then executed by the server.

85
Q

What is social engineering?

A

Umbrella term covering different manipulation techniques that exploit human error, with a view to obtaining private information, access to a restricted system or money.

86
Q

What are 8 of the social engineering scams?

A
  • Baiting.
  • Scareware.
  • Pretexting/blagging.
  • Phishing.
  • Pharming.
  • Shoulder-surfing.
  • Quid pro quo.
  • Vishing.
87
Q

What is Phishing?

A

Online fraud technique used by cybercriminals to trick users into giving out personal information, e.g. usernames, passwords, credit card details.
Perpatraitors disguised as a trustworthing source in an electonic communication such as an email or fake website.

88
Q

What is Pharming?

A
  • “Phishing without a lure”
  • Malicious code installed on a PC or server misdirects users to fraudulent websites without their knowledge.
89
Q

What is a firewall?

A

Piece of software or hardware (sometimes both) configured to let only certain types of traffic through it, aswell as block certain ports. Can also inspect data travelling across it to see if it looks suspicious.
(Operating systems and home routers come with built-in firewalls)

90
Q

What 2 things can a firewall be set up to prevent?

A
  • Unauthorised internet traffic from outside a LAN.
  • Users in a LAN from accessing parts of the internet prohibited by the company they work for.
91
Q

What are the 5 rules to creating a secure password?

A
  • A minimum length.
  • Uppercase & Lowercase & Numbers.
  • Can’t be the same as your last x passwords.
  • Must be changed every x days.
  • Cant be based on a name.
92
Q

What is common method to preventing unauthorised access to a system?

A

Requiring users to log in with predetermined credentials such as a username + password.
Can be more secure by implementing password rules but enforcing them causes users to write them down defeating the objective.

93
Q

What is a common way to prevent/minimise threats?

A
  • Installing anti-malware software.
  • Often pre-installed with your operating system.
94
Q

Why should you always update systems/software?

A

When first released, far from perfect and can include bugs or flaws which can be exploited by malware.

95
Q

What are patches?

A

The fix developed by the company after they have discovered a flaw.

96
Q

What is a proxy?

A
  • A physical device between a network + remote source.
  • Ensures no direct/physical connection between a single user and a remote source.
  • Has the ability to look at a web page & its contents and choose whether to pass it back to the user.
97
Q

What is encryption?

A
  • Process of turning plain text into an unreadable form.
  • The plain text is encrypted using an algorithm and a unique key.
  • Only if you have the appropriate key can you translate the cyphertext back into readable form.
98
Q

What is considered to be a weak point in any computer system?

A
  • People.
  • Can be mitigated through user training + education programs but never eliminated entirely.
99
Q

What are 10 weaknesses of people?

A
  • Sharing passwords.
  • Losing memory sticks/laptops.
  • Writing passwords down on sticky nodes attatched to computers.
  • Leaving printouts on desks.
  • Not installing operating system updates.
  • Not logging off or locking computers.
  • Not keeping anti-malware up to date.
  • Not locking doors to computer rooms.
  • Not applying secuirty to wireless networks.
  • Not encrypting data.
100
Q

What does a modem do?

A

It transforms digital information from your computer into analogue signals that can be transmitted through wires.
It can also translate analogue signals back into digital data your computer can understand.

101
Q

How does a modum do the information transformation?

A

By modulating and demodulating electrical signals sent through phone lines, coaxial cables + other types of wiring.

102
Q

What are the 2 ports a standard modum has?

A
  • One connecting to the outside world.
  • An ethernet port that connects to a computer/router.
103
Q

What is a router responsible for?

A

Routing data:
- Between devices on a small home network.
- Between devices on a network and the internt.

104
Q

How is a router connected?

A

A modum is connected to one port (often labelled WAN). Your devices connect to the other ports or wirelessly using the Wi-FI standard.

105
Q

What are the two main methods for connecting devices?

A
  • Wired.
  • Wireless.
106
Q

What are the three most popular cables>

(For physical wired connections)

A
  • Twisted pair.
  • Coaxial.
  • Fibre optic.
107
Q

What are the 5 characteristics of a twisted pair cable?

A
  • Made of a pair of insulated copper wires.
  • Cables can be affected by noise from external magnetic fields.
  • More affordable than coaxial + fibre optic.
  • Only able to provide low bandwidth.
  • Used for telephone networks, data networks and cable shielding.
108
Q

What are the 4 cylindrical components making up a coaxial wire.

A
  • (inside -> outside); a sold conductor wire, a layer of insulation, a grounding conductor and a layer of exterior insulation
109
Q

What are the 4 characteristics of Coaxial cables?

A
  • Can be affected by noise from external magnetic fields. (To a lesser extent than twisted pair).
  • Provides moderate bandwidth.
  • More expensive than twisted pair & cheaper than fibre optic.
  • Used for feedlines that connect radio transmitters and recievers to antennas as well as computer network connections, digital audio and cable television.
110
Q

What are fibre optic cables made out of?

A

Very thin optical fibres bundled together into a single cable. the fibres can be either glass or plastic.

111
Q

What are the 3 characteristics of fibre optic cables?

A
  • Highest noise immunity (As light rays are unaffected by electrical noise).
  • High bandwidth so most expensive.
  • Used to support long-distance connections between cities and countries, as well as data centres and organisations transmitting large volumes of data.
112
Q

What is a Network Interface Controller (NIC)?

A

It allows both wired + wireless communication between computers on a LAN or connected to a large-scale network using the internet protocol (IP).
Without it a computer cannot connect to a network.

113
Q

What 2 layers is the network interface controller?

A
  • The physical layer + data link layer.
  • Provideds the necessary circuitry for physical layer processes and some data link layer processes to run on it.
114
Q

What does a wireless access point (WAP) do?

A
  • Creates a wireless local area network (WLAN), usually in a home or office building.
  • It connects to a wired router, switch, or hub via an ethernet cable and projects a Wi-Fi signal within a designated area.
115
Q

Why would a business use multiple WAPs?

A

Because Wi-Fi range is limited and easily interrupted by various construction materials.

116
Q

What are 2 features of a hub?

A
  • Allows you to connect multiple devices to one network.
  • Only a hardware device (no software)
117
Q

How does a hub work?

A

Operates on the physical layer and is considered a passive device; it simply broadcasts the transmission it recieves to all other connected devices.

118
Q

What are the 2 disadvantages of a hub?

A
  • Network can easily become flooded with unnecessary traffic.
  • Typically slower than switches when transfering data.
119
Q

What is a switch?

A

A device allowing you to connect multiple devices to one network.

120
Q

How does a switch work?

A

It operates on the data link layer and is an active device; it can inspect transmissions and route them to the correct device.
It has software for administration + configuration purposes.

Computer Science JA (9 decks)

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