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Computer Science AS level OCR > 1.3.3 > Flashcards

1.3.3 Flashcards

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1
Q

network

A

A network is the name given to two or more computers connected together with the ability
to transmit data between each other. There are two main types of networks: local area
networks and wide area networks.

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2
Q

network adv and dis

A
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3
Q

WAN

A

Wide Area Network
- Collection of connected computers/devices over a large geographical area
Large corporations with offices in multiple locations will often have a WAN allowing them to communicate between different sites.
Multiple LANs physically located in different areas form a WAN.
Typically, connected by: telephone lines, fibre optic cables, satellite links
Usually, a WAN will require extra telecommunication
hardware.

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4
Q

LAN

A

Local area network (or LAN) is the name given to a network which is spread over a small
geographical area or a single site, for example: a school.
All hardware for LAN tends to be owned/controlled by organisation using it.
Typically connected using: UTP cable, fibre optic, Wi-Fi

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5
Q

standards

A

are a set of hardware and software specifications that allow manufactures to crate products and services that are compatible with each other.

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6
Q

protocols

A
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7
Q

Explain why protocols are important on a network

A

Allowing them to communicate
- By ensuring all devices follow the same rules/standards
- So they interpret data/signals in the same way

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8
Q

common protocols

A
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9
Q

TCP/IP protocol stack

A
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10
Q

UDP

A
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11
Q

HTTP/HTTPS

A
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12
Q

FTP

A
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13
Q

POP/IMAP/SMTP

A
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14
Q

purpose of layering

A

concept of layering is to divide complex task of networking into smaller simpler tasks that work in tandem with each other. The hardware/software for each layer had defined responsibility, and each one provides a service for the layer above it.
ADV:
reducing complex program into smaller sub problems makes it easier to understand.
Devices can be manufactured to operate a particular layer.
Products from different vendors will work together.

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15
Q

four layers of the TCP/IP stack

A

-Application
-Transport
-Internet
- Link

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16
Q

application

A

Based at the top of the stack, this uses an appropriate protocol relating to whatever application is being used to transmit data. It specifies what protocol needs to be used to relate the application that’s being sent. E.g. a message being sent via a web browser, protocols would be HTTP, HTTPS, FTP.

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17
Q

transport

A

Uses TCP part of the stack as well as other conversation protocols like UDP, to establish an end-to-end connection between the source and recipient computer.
These protocols use port numbers to track sessions and add this information to the header. Once the connection is made, the transport layer splits the data into packets, adding to each one:
- Its number/sequence (they are numbered so they can be reassembled in the correct order).
- Total number of packets
- Port number that the packet should use
If any packets get lost, the transport layer requests retransmissions of these lost packets.

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18
Q

internet

A

Uses IP part of the stack.
Adds to each packet:
- Source IP address
- Destination IP address
The combination of the IP address and the port number is called a socket address.
All routers operate at this layer, they use the IP address to find out where the packets are heading.
○ Routers operate on the network layer and the router is what uses the IP addresses to forward the packets.
○ The sockets are then used to specify which device the packets must be sent to and the application being used on that device.
We know now:
- The device the packet is being sent to (IP address).
- The application on that device that needs the packet (port).

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19
Q

link layer

A

Represents the actual physical connection between network devices.
Responsible for adding the unique media access control (MAC) address of the:
- Source device
- Destination device
When transmitting data between routers over a wide area network (WAN) , the MAC address is changed at each hop on the route.

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20
Q

example of TCP/IP

A
21
Q

modem

A
22
Q

router

A
23
Q

cables

A
24
Q

cables twisted

A
25
Q

cables coaxial

A
26
Q

cables fibre optic

A
27
Q

NIC

A
28
Q

WAP

A
29
Q

HUB

A
30
Q

switch

A
31
Q

client server

A

Client-server networks consist of terminals known as clients connected to a server.
The server is a powerful, central computer. The server holds all of the important information and resources and has greater processing power than the terminals.
Clients can request to use the server.
Best suited to organisations with a large number of computers/computers needs to access the same info.

32
Q

client and server jobs

A
33
Q

client serves adv and dis

A
34
Q

peer to peer jobs

A
35
Q

peer to peer

A

A network in which computers are connected to each other so that they can share files. Each device effectively acts as both a server and client, as it can both provide and request
resources.
Best suited for smaller organisations with fewer computers or where fewer users need to access the data.

36
Q

world wide web

A

The interet provides many services- popular one is WWW.
WWW is a collection of files with info stored in hypertext, and otehr associated files, hosted on web servers.
These web servers store the files and handle clientrequests.
A web page, stored as text(HTML, CSS, JavaScript, is sent to a web browser application, which uses rules to render it right.

37
Q

Domain name system

A
38
Q

network security

A

when connecting computers together via a network, allowing them to share data and connecting them to the internet, they become vulnerable to misuse/attacks.
aim is to only allows authorised access to what they need.
prevent unauthorised access
minimise the potential damage caused by unauthorised damage.

39
Q

security issues and threats - hackers

A

hacker: person who attempts to gain access to a computer system with the intent of damaging data/harming system.
Black hat hackers: attempt to gain access via nefarious means, steal companies secrets/cause damage.
White hat hackers: security experts employed by company, ethical hackers that use their expertise to find vulnerabilities sand fix them.
Grey hat hackers: between the two not employed but attempt to locate flaws in companywide computer systems. technically illegal but inform company to fix them.

40
Q

secure issues and threats- malware

A

Malware: computer code written with the intent to harm/frustrate.
Can have a wide range of effects depending on its type:
Deleting, corrupting or encrypting files.
causing computers to crash, reboot/slow down.
reducing network speeds.
logging keyboard inputs and sending them to hackers.
virus: most well-known malware, pieces of code capable of copying themselves and spreading throughout the system. typically designed to have a detrimental effect like corrupting a file system/destroying data.
spyware- form of malware that covertly obtains info about users’ computer activities by transmitting data from their device. Used in a variety of ways to get sensitive/personal data:
internet surfing habits, email addresses, visited web pages, downloads, passwords, credit card numbers, cookies.

41
Q

Security issues and threats-dos

A

denial of service attack
DoS is when an attacker floods a server with useless traffic, causing server to become overloaded. exploit limitations of TCP/IP stack.
Attacks often target web servers of high-profile organisations (banks/government). Don’t typically result in theft/loss of Clara but take a lot of money and time to handle.
Can happen without device owner’s knowledge.

42
Q

Security issues and threats - SQL injection

A

Code injection technique used to attack data driven applications. Attack designed to exploit vulnerability poorly coded applications. Code entered in input text boxes and executed by the server.

43
Q

Security issues and threats- social engineering

A

Several different restricted system/money. These scams lure users into exploiting data, spreading malware / providing access to a system. Scams include: baiting, scareware, phishing, charming, vishing, pre texting.
Phishing - online fraud technique used by cyber criminals to trick users into giving out personal info: usernames/passwords/ credit card details. Disguise themselves as a trustworthy source in an electron communication .
Pharming- online fraud technique red by cyber criminals. Malicious code installed on pc/server and misdirects users to fraudulent websites their knowledge.

44
Q

Preventing and minimising threats -firewalls

A

Piece of software/hardware configured to let only certain types of traffic through A. Set up to prevent: enthused internet traffic from outside LAN, users in LAN from accessing parts of the internet prohibited by the company they work for.
Can block certain ports / type of traffic and inspect data travelling across it to see if it looks suspicious. Os and home routers come with built in ones + can buy more sophisticated ones.

45
Q

Preventing and minimising threats - secure password system

A

Requiring users to log in with predetermined credentials username and password.
Can be made more secure by implementing password rules.
Can’t be name, uppercase and lowercase, minimum length.

46
Q

Preventing and minimising threats - up to date software and anti malevave sothuare.

A

Installing anti-malware software, ensuring suflwave such as operating system and AMS is always updated with latest version- more developed/prevent more bugs.

47
Q

Preventing and minimising threats- proxies

A

Physical device placed between a network and a demote source. Example can handle web page requests, if its not on proxy’s band list, it will pass request. Can look at page and it contents and choose whether to pass it back to user. Ensures there is no direct/physical connection between a single oor and a remote source.

48
Q

Preventing and minimising threats - encryption

A

Process of turning plain text to an unreadable form. Using an algorithm and a unique key. Only someone with the appropriate Key will be able to translate the text back into readable form.
Won’t stop you from being hacked but will make any stolen data difficult to read.

Computer Science AS level OCR (20 decks)

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