1.3.3 Networks Flashcards
Define a network
Two or more computers connected together, to share information and resources
Define a LAN
Local Area Network:
A connection of devices
In a small geographical location
What are the advantages of a LAN?
- Enables privacy from the outside world
- Can control the access to data/programs
- Can control the access to devices
What are the disadvantages of a LAN?
- Requires some expertise to install and maintain
- Can be costly for a larger LAN
- Unauthorised access to data depends on personnel and their security measures
Describe the role of an NIC
Network Interface Card:
Converts data signals from a node into one that can be transferred over a network
Describe the role of a switch
Connects all the nodes together; intelligent so can send data packets only to their intended destination
Describe the role of a hub
Connects all the nodes together; not intelligent so data packets are transmitted across the whole network
Describe the role of a router
Manage data packets, enabling them to be sent between networks
Describe the role of a WAP
Wireless Access Point:
Allows nodes to connect to the network wirelessly
What is the difference of a client-server network over a peer-to-peer network?
- A computer is designated as the server, rather than all having the same status
- Server manages network traffic and data requirements, thus having less collisions and being faster
- Larger networks have more servers, this can handle a greater network demand
- Popular of companies, rather than home networks
Advantages and disadvantages of a bus network topology
- Cheap, due to all nodes being connected to one cable
- Data collisions slow the network - travels both ways
- Whole network suffers from cable faults
- Only useful over small areas
Advantages and disadvantages of a ring network topology
- Cheap: only one cable
- One-way data travel - no collisions
- Whole network suffers from cable faults
Advantages and disadvantages of a star network topology
- Other nodes are unaffected from a cable fault
- Can be costly with large number of nodes
- Network will slow with multiple nodes requesting data or software at the same time
Advantages and disadvantages of a mesh network topology
- Every node is connected
- Other routes are available to combat high network traffic or cable faults
- Very expensive: large amounts of cabling required
What is the difference between a LAN and a WAN?
LAN: Located on one site, owner owns the network devices
WAN: Covers a large geographical area, devices can be provided by telecoms companies
Explain ‘Web Hosting’
A computer on a network: serves users of the internet as a host.
Websites are usually hosted on servers for people to access them (sometimes for a fee)
Explain ‘IP address’
Internet Protocol Address:
A unique number given to every computer on the internet.
Identifies the computer, may change each time a network is joined
Explain ‘ISP’
Internet Service Provider:
The company who provides you with an internet connection
Explain ‘URL’
Uniform Resource Locator:
The name for a web adress
Explain ‘DNS’
Domain Name System:
The system used to find the computer hosting the required website
Explain ‘the Cloud’
A network of servers hosted on the internet, offering a range of services for data
How does a DNS work?
- The website’s URL is entered
- The URL is sent to the ISP, where it is looked up in their DNS’s address book
- The required IP address is returned to you, to communicate to the computer hosting the website
Advantages of the Cloud
- Don’t need to buy and install software
- Any connected device can access the service
- No need to upgrade software
- Collaborative documents can be formed
- Work is saved automatically
Disadvantages of the Cloud
- Sensitive data stored in other countries may be under different data laws
- Can be less secure than local storage
- Completely reliant upon the network/internet
What is the role of an internet registrar?
- Holds the details of domains available for purchase
- Registers company details
- Resolves domain name disputes
How are files sent over the internet?
They are split into data packets before being transmitted
What are the components of a data packet?
Data
Error check
Packet header
Describe the Error check within a data packet
Includes a checksum number: a calculation for checking if all the data has arrived uncorrupted
Describe the Packet header within a data packet
Sequence number: for data packets to be put back together in the right order
Return address: when needed to notify the sender’s computer if the packet has been received or has been corrupted
Destination address: so the packet arrives in the correct location
Define a protocol
A set of rules for devices to follow
Describe a MAC address
(Media Access Control) Hard-coded into each networked device, so data can be sent to the correct node’s NIC
Describe the features of an IP address
Used so data on a WAN is sent to the correct network/node
Dynamic: changes whenever you connect to a network
Describe TCP/IP
- Transmission Control Protocol / Internet Protocol determines how data is sent over the internet
- TCP: defines rules for splitting up packets, ensures data is split apart and put together the right way
- IP: ensures data packets are directed towards their destination in the most appropriate way
Describe ‘Packet Switching’
- TCP splits a file in packets
- IP directs packets through routers
- Packet switching occurs by packets being directed to other routers on their journey
- TCP reassembles the packets per their sequence number
Describe ‘Circuit Switching’
When two devices are connected by a dedicated communication channel.
- Data is sent in-order for no receiving delay
- Wastes bandwidth as others cannot use the same channel
Describe HTTP
Hyper Text Transfer Protocol:
Governs the way websites and web servers are accessed by web browsers
Describe HTTPS
HTTP Secure:
Ensures all data being sent is encrypted
Describe FTP
File Transfer Protocol:
Governs the way stored files are accessed from a server
Describe POP
Post Office Protocol:
Governs how emails area accessed from a server
Describe IMAP
Internet Message Access Protocol:
Similar to POP, and with emails remaining in the server after the client downloads it, e.g. for multiple devices
Describe SMTP
Simple Mail Transfer Protocol:
Governs how data is sent between mail servers
What are the 4 protocol layers?
Application layer - layer 4
Transport layer - layer 3
Network layer - layer 2
Data Link & Physical Layer - layer 1
Describe the 4th protocol layer
Application layer: FTP, HTTP, HTTPS, POP, IMAP, SMTP
Provides user access to applications, websites, files, and emails
Describe the 3rd protocol layer
Transport layer: TCP
Provides transport of data between devices by splitting files into data packets
Describe the 2nd protocol layer
Network layer: IP
Provides the routing of packets across the network by addressing
Describe the 1st protocol layer
Data Link Layer & Physical Layer: Ethernet
Provides the physical transport of data through electrical signals
Explain physical protocols
These govern how data is sent through physical mediums.
E.g.:
- Wired or wireless transmission
- Copper or fibre optic cabling
Explain logical protocols
These govern the data that is being sent
E.g. bit rate, error checking, ordering of packets, compression and encryption, digital signatures
Describe ‘handshaking’
- Two devices communicating over the internet will decide on which protocols to use
- One device sends a list of protocols, the other sends acknowledgement or rejects them and another is chosen
What is the difference between a MAC address and IP address?
MAC: fixed to a device when on a LAN
IP: dynamic to a LAN or device on a WAN
Describe ‘virus’
Small programs which cause physical harm to a computer system
E.g. standard virus, worm virus, trojan virus
Describe ‘standard virus’
Hides in programs and replicates itself to spread. Aims to delete or damage data
Describe ‘worm virus’
Replicates itself to use more of the computer’s resources
Describe ‘trojan virus’
Often causes harm in the background, e.g. creating backdoors, deleting data, changing setups
Describe ‘spyware’
Watches the user’s activity and sends back information
Describe ‘adware’
Downloads and displays unwanted adverts and collects marketing information. Tries to direct you to unwanted websites
Describe ‘ransomware’
Locks your computer, demanding money to get it working again
Describe ‘rootkit’
Contains tools to allow criminals to access your computer at administrator level
Describe ‘pharming’
Seeks to change a stored IP address to send you to a fake website
Describe ‘phishing’
Tries to acquire sensitive information through direct communication by impersonation
Describe ‘people’ in relation to network threats
A lack of knowledge leads people to be more susceptible to threats when influenced to give away information
Describe ‘brute force attacks’
Using trial and error to hack an account
Describe ‘denial of service’
Attempting to bring down websites by using up the web server’s resources: repeatedly tries to access the website
Describe ‘data interception and theft’
Using specialist hardware and software to secretly monitor network traffic.
Can intercept packets.
Describe ‘SQL injection’
Attaching SQL commands to a password to alter the SQL statements, allowing access to other accounts or data
Describe ‘poor network policies’
A set of rules and procedures that network users must follow.
If it is poor or not followed properly then the risk of a breach is increased.
Describe ‘penetration testing’
A company will invite an expert to simulate a range of network attacks. This attempts to discover weaknesses
Describe ‘network forensics’
Networks should have software continually monitoring network traffic. This helps with finding the source of attacks
Describe ‘network policy’
An Acceptable Use Policy, Backup Policy, and Disaster Recovery Policy should exist. These sets of rules govern how the network is used and maintained
Describe ‘anti-virus/-malware software’
Software dedicated to finding and destroying viruses and malware.
Must be kept up-to-date
Describe ‘firewall’
This will monitor data packets flowing into a computer.
Packets are received by ports, and the firewall opens ports where data is expected to come to
Describe ‘proxy server’
A computer which receives internet requests, analyses them against a set of protocols, then sends it out - intermediary
Describe ‘encryption’
Data is converted from plaintext to cyphertext with an encryption key before being sent on a network
Describe ‘user access levels’
Users of a system will have different rights depending on their role in the company. This changes what they have access to
