Networks Flashcards
COMPUTER NETWORKS
What is a computer network?
A computer network is 2 or more devices connected to communicate and share resources.
Advantages of a computer network:
○Share data
○Share storage
○Share internet
○Share peripherals
○Files can be shared easily between users
○Data is easy to backup as all the data is stored on the file server
○Site (software) licenses are likely to be cheaper than buying standalone licenses
Disadvantages of a computer network:
○Hacking
○Security
○Purchasing the network cabling and file servers can be expensive
○Viruses can spread to other computers throughout a computer network
○A danger of hacking, particularly with WANS. Security procedures are needed to prevent abuse > firewall
WAP
Wireless access point, uses a radio transceiver to allow wireless connections to a network. In effect, the WAP creates its own wireless network, which devices connect to. The WAP then sends wireless traffic it receives onto the main wired network. WAPs can also be used to extend the range of a wireless network.
NIC
Network interface card, a circuit board installed in a computer to allow it to be connected to a network.
Router
One of the most commonly used connection devices. They are used to send data signals across the internet. Routers work by collecting knowledge of available routes to transmit data. They then determine the most suitable route for sending data.
Switch
Switch connects various devices in a network.
TYPES OF NETWORKS
What is a PAN?
Personal Area Network - covers a very small area.
Examples- Cell phones, headsets, wireless keyboards, wireless mice, printers, barcode scanners, game consoles.
What is a LAN?
Local Area Network - covers a small geographical area.
Examples- Schools, offices, colleges, homes
What is a WAN?
Wide Area Network - covers a large geographical area.
Examples- Internet, organisations that have more than one office or branch, national telephone infrastructures or via wireless transmission, banks
What is a WLAN?
Wireless Local Area Network
TOPOLOGIES
Star topology:
All nodes indirectly connect to each other through one or more switches.
The switch acts as a central point through which all communications are passed.
Large networks using a star topology are usually controlled by one or more servers.
Peer-to-peer networks can also have a star topology.
Advantages of a star topology:
○If one device fails, the rest of the network is unaffected
○There are fewer data collisions
Disadvantages of a star topology:
○The cost is expensive-have to buy specialist hardware
○You can add a certain number of devices depending on the number of possible connections on the network determined by the switch
Bus topology:
All nodes in the network are connected directly to a central cable that runs up and down the network.
This cable is known as the backbone.
Data is sent up and down the backbone until it reaches the correct node.
It is easy to connect nodes to the network.
Less cabling is needed compared to a star topology, making it cheaper to install.
Advantages of a bus topology:
○If one device fails, the whole network is unaffected
○It doesn’t have a switch-cheap
Disadvantages of a bus topology:
○Data collisions are more frequent
○If the main cable breaks it can split the network into 2 or shut the entire network down because there will be a lot of reflected signals-reliant on the main cable
TCP/IP MODEL
Sending data:
Application layer > Transport layer > Internet/network layer > Link/Data link layer
Receiving data:
Link/Data link layer > Internet/Network layer > Transport layer > Application layer
Application layer:
○Opening web browser > software
○Where the software operates: web browsers, email services
Protocols used: ○HTTP ○HTTPS ○FTP ○IMAP ○SMTP
Transport layer:
○Setting up the communication between 2 devices. Splitting data into packets and checking packets are correctly sent and delivered
Protocols used:
○TCP
○UDP
Internet/Network layer:
○Adds IP addresses to data packets then directs them between devices using routers
Protocols used:
○IP > used by the router
Link/Data link layer:
○Where the hardware and drivers operate. Passes data over the physical network, such as ethernet cable, WIFI signals, NICs
Protocols used:
○Wi-Fi
○Ethernet
PROTOCOLS
What are protocols?
Protocols are a set of rules for how devices communicate across a network.
Ethernet
Ethernet is a protocol that describes how data is transmitted in wired networks.
HTTP
Hyper Text Transfer Protocol > used by web browsers to access websites and communicate with web servers.
HTTPS
HTTPS Secure > a more secure version of HTTP. Encrypts all information sent and received.
FTP
File Transfer Protocol > used to access, edit, and moves files between devices on a network. eg. to access files on a server from a client computer.
IMAP
Internet Message Access Protocol > used to retrieve emails from a server.
SMTP
Simple Mail Transfer Protocol > used to send emails. Also used to transfer emails between servers.
TCP
Transmission Control Protocol > establishes a connection between the sending and receiving devices, splits data into packets, and numbers the packets.
TCP is better when you need a reliable connection.
UDP
User Datagram Protocol > breaks the data down into packets without numbering them.
UDP is suitable for applications that need fast, efficient transmission.
MALWARE
Spyware:
Secretly tracks user actions, such as key presses. Software that observes activities. Key logger-track activities. Sensitive information ○personal information ○bank details ○passwords
Worms:
Can spread from device to devices.
Unlike viruses, they don’t need to attach themselves to other programs.
Can copy themselves hundreds of times, so they can quickly harm devices.
Exploit weaknesses in network security.
Self-replicates (person is not needed for the worm to replicate) faster.
Trojan (horse):
Pretends it will be an useful and safe program, when actually it will try to hack your device.
Disguises itself on a legitimate software.
Installed without realising.
Virus:
Spreads by copying itself to normal programs.
Users spread them by copying infected files and activate them by opening infected files.
Files/Software/Computers
Person is needed for the virus to replicate.
SECURITY THREATS
Patched/Outdated Software:
○Can be exploited more easily by hackers, malware and viruses.
○Automatic Software Updates are used to patch (fix) any identified security holes in a piece of software.
Misconfigured Access Rights:
○MAC address filtering is a way of making sure the only people on a network are trusted users.
○Checks the unique identification of each device that tries to connect to the network and only lets allowed devices join the network.
○Some people can see some things others can’t.
Weak/Default Passwords:
○Can be more easily cracked.
○Hackers can use brute force attacks to get past short or simple passwords easily.
○Hackers use social engineering to figure out commonly used passwords (birthdays or addresses).
Removable Media:
○Refers to storage devices that can be removed from the computer system
Examples:
○USB
○Hard drives
○DVD’s
○External hard drives
○If removable media contain malware, it will attempt to move onto a system when connected to a computer, and then onto any other connected devices.
○If a computer is connected to others on a network, this could mean that the virus reaches hundreds of machines.
SOCIAL ENGINEERING
Phishing:
When criminals end emails or texts to people claiming to be from a well-known business.
The link is the bait.
Gain access to personal information.
Pharming:
Where an user is directed to a fake version of a website that looks like the real thing.
Often carried out using malware.
Blagging:
When someone makes up a story or pretends to be someone they’re not to persuade the victim to share information.
Lying to manipulate you to give out their personal information.
Shouldering:
When someone is observing and watching a person’s activity.
Examples - spying someone’s PIN number at a cash machine, or someone putting their password in a secured computer, typing in personal information.
There are camera’s at cashpoints.
List the measures that can be used to maintain the security of a computer system.
For each measure:
○Outline what the measure is.
○Explain what types of threat to cyber security it is effective
against.
Virus checker:
Outline:
○Scans files to look for malicious code.
○Needs to be updates regularly with latest virus definitions.
○Can quarantine/delete malware/suspicious files.
Effective against:
○Malware
List the measures that can be used to maintain the security of a computer system.
For each measure:
○Outline what the measure is.
○Explain what types of threat to cyber security it is effective
against.
Firewall:
Outline:
○Analyses/scans network traffic.
○Can block traffic from suspicious hosts/computers/addresses/ports.
Effective against:
○Hackers
○Transmission of malware
List the measures that can be used to maintain the security of a computer system.
For each measure:
○Outline what the measure is.
○Explain what types of threat to cyber security it is effective
against.
Login system/Authentication/Password/Biometric:
Outline:
○User has to enter username and password.
○Can be authenticated by other methods such as biometrics.
○Login details matched to a database of users.
Effective against:
○Hackers
○Unauthorised access
List the measures that can be used to maintain the security of a computer system.
For each measure:
○Outline what the measure is.
○Explain what types of threat to cyber security it is effective
against.
MAC address filtering:
Outline:
○Each hardware device has unique hardware address.
○A database of allowed hardware/MAC addresses is kept/whitelist.
○To connect to a network a device must have an address on the address on the database/whitelist.
Effective against:
○Unauthorised devices
List the measures that can be used to maintain the security of a computer system.
For each measure:
○Outline what the measure is.
○Explain what types of threat to cyber security it is effective
against.
Encryption:
Outline:
○Data is stored/transmitted as ciphertext (A. in coded form).
○Only people who know the encryption method/key can decrypt/read the data.
Effective against:
○Data theft
List the measures that can be used to maintain the security of a computer system.
For each measure:
○Outline what the measure is.
○Explain what types of threat to cyber security it is effective
against.
Prevention of use external storage devices/USB ports:
Outlines:
○Ports on a computer are disabled.
○Storage devices connected to them cannot be accessed//flash drives cannot be used.
Effective against:
○Putting malware onto a computer
○Theft of data
List the measures that can be used to maintain the security of a computer system.
For each measure:
○Outline what the measure is.
○Explain what types of threat to cyber security it is effective
against.
Access rights:
Outline:
○Users are associated with certain privileges.
○These might control files that can be accessed/run //level of internet access//ability to create/delete files//ability to change settings.
Effective against:
○Hackers
○Theft of data
○Authorised users doing unauthorised things
List the measures that can be used to maintain the security of a computer system.
For each measure:
○Outline what the measure is.
○Explain what types of threat to cyber security it is effective
against.
CAPTCHA:
Outline:
○Users have to type in some distorted text//recognise images for a set of images.
○Humans can do this but it is a difficult task for computer programs/bots.
Effective against:
○Automated hacking programs
○Bots
List the measures that can be used to maintain the security of a computer system.
For each measure:
○Outline what the measure is.
○Explain what types of threat to cyber security it is effective
against.
Automatic software updates:
Outline:
○Operating system/software configurated to download updates from the internet.
○Hackers look for security vulnerabilities in software.
○Updates can patch (fix) security vulnerabilities.
Effective against:
○Hackers
○Malware
