9.3 The Internet Flashcards
what is The internet?
A network of interconnected computer networks which uses an end-to-end communication protocol.
How is the internet connected?
It is mostly a wired network with cables that pass under oceans to connect the different continents.
What is an internet service provider (ISP)
A company that provides its customers with access to the internet.
What is a packet in terms of the internet?
A container in which data is transmitted over networks. They’re labelled with addresses for the sender and the recipient and contain information intended for the recipient.
What is the role of packet switching and routers?
One message is frequently split into multiple packets, each of which is sent to its
recipient via the best possible route. Packets are reassembled with other packets that form part of the same message by their recipient. Packets usually have to pass through number of routers before reaching their destination. Packets’ recipient addresses are used by routers to determine where to send them. Every time that a packet passes through a router, a hop is said to occur. A packet’s time to live (or TTL) is a number that indicates how many hops the
packet can partake in and is reduced by one with each hop. When a packet’s TTL expires, the packet is dropped. The recipient will notice a missing packet and request that the sender transmits the missing packet again
Explain what a packets time to live (TTL is)?
Holds the number of hops a packet can go through before
being dropped
What are the primary components of a packet?
Sender’s address, receiver’s address, packet contents, time to live (TTL), sequence number
Explain the purpose of a packet’s sender’s address?
Identifies where the packet was sent from, and therefore where the response should be sent to.
Explain the purpose of a packet’s receiver’s address?
Identifies the packet’s intended recipient, allowing it to be routed to the correct device.
Explain the purpose of a packet’s contents?
Where the packet holds the data that is being transferred
Explain the purpose of a packet’s sequence number?
Contains the number of packets in a message and identifies a packet’s position in relation to others.
What do routers and gateways do together?
They connect different networks, allowing packets to reach their destination.
Explain what a router does?
Send packets to their recipient via the fastest possible route. They hold tables with information relating to the fastest routes to certain devices.
Explain what a gateway does?
As two networks could use different protocols, packets must be modified so they conform to both protocols. Gateways strip away most of the packet’s details, leaving just the packet’s contents. The gateway will then give packets new sender and receiver addresses which comply to the new protocol.
What is a uniform resource locator (URL)?
An address assigned to files on the internet. Different protocols can be used in URL’s to access different types of files in different ways.
In the URL (https://ww.bbc.co.uk/news/technology/index.html) explain the purpose of “https://”?
It is the protocol being used to access the file.
In the URL (https://ww.bbc.co.uk/news/technology/index.html) explain the purpose of “www”?
It is the subdomain for world wide web.
In the URL (https://ww.bbc.co.uk/news/technology/index.html) explain the purpose of “bbc.co.uk”?
It is the domain.
In the URL (https://ww.bbc.co.uk/news/technology/index.html) explain the purpose of “/news”?
It is the directory of the file being requested.
In the URL (https://ww.bbc.co.uk/news/technology/index.html) explain the purpose of “/technology”?
It is the subdirectory of the file being requested.
In the URL (https://ww.bbc.co.uk/news/technology/index.html) explain the purpose of “/index”?
It is the name of the file being requested.
In the URL (https://ww.bbc.co.uk/news/technology/index.html) explain the purpose of “.html”?
It is the file’s extension.
What is the purpose of a domain name?
Identifies an organisation or individual on the internet. They use alphanumeric characters which make them easy for humans to remember.
what is a fully qualified domain name (FQDN)?
A domain that specifies an exact resource and can be interpreted in only one way. An FQDN will always include the servers host name. For example “www”.
What uses an internet protocol (IP) address?
Every computer on the internet and every device that communicates on a network.
Explain the purpose of domain names?
As IP addresses are not easy for humans to remember, domain names are used. They map to IP addresses, meaning they are a human-friendly representation of an IP address.
Explain the functionality of a domain name server (DNS)?
A domain name server is used to translate domain names into their corresponding IP address. It stores a table of domain names and their corresponding IP address
What is the role of an internet registry?
To protect the world’s depleting pool of unallocated IP addresses. When a new IP address is requested an Internet registry will first look for a previously allocated IP address that has become unused rather than allocate a brand new IP address straight away.
What does a firewall do?
Sits between a device and the internet and regulates the packets that pass through it. Firewalls can be software or hardware and work as a proxy server which can perform both packet filtering and stateful inspection.
How does packet filtering work and what does it do?
Firewalls use packet filtering to accept and block packets based on their source IP address or the protocol that they are using. A network’s administrator can specify particular IP addresses or protocols to block or use automatic filtering software that can block suspicious packets.
What is stateful inspection and how does it work?
Stateful inspection actually examine the content of a packet before deciding whether to allow it through the firewall. Some firewalls keep a record of current in a network, allowing them time to filter out packets that aren’t related to activity on the network.
What is a proxy server and what do they do?
A server that sits between a public network and a private network. They manage every packet that passes between the two networks. Firewalls can be said to act as proxy servers when they control the movement of packets between public and private networks.
How do firewalls provide anonymity?
When a device in a private network sends a packet through a firewall and into a public network, the packet’s “sender” address is that of the firewall, rather than the devices private IP address. Provides anonymity to devices on privates networks as their private address is never sent beyond the private network.
How does symmetric encryption work?
Both the sender and receiver share the same private key. The key is used to both encrypt and decrypt data sent between the two parties.
Before sending any information the sender and receiver must participate in a key exchange to ensure that they both have a copy of their shared key.
What is the disadvantage of symmetric encryption.
If the key exchanged over a network, it is vulnerable to interception.
How does asymmetric encryption work?
Each device has a pair of mathematically related keys. One key is kept private (private key) and the other is shared on the internet (public key). When a message is encrypted with a public key, only the corresponding private key can decrypt it and vice-versa. Before a message is sent it is encrypted by the sender using the recipient’s public key. The message can only be decrypted by the corresponding private key, the recipient’s private key. Only the recipient has access to this key so the recipient is the only person who can decrypt the message.
when are digital signatures used?
When using asymmetric encryption, it can be used to verify the sender of a message and to verify that a message has not been tampered with during transmission.
What are the 4 stages of digital signature encryption?
1) digest of the message is created
2) the digest is encrypted with the sender’s key
3) The encrypted with the sender’s private key
4) The message and appended digest are encrypted with the recipient’s public key
How does digital signature decryption work?
When the recipient receives the message, they:
○ decrypt the message using their private key
○ decrypt the digest using the sender’s public key
○ carry out the same digest algorithm on the message
○ check whether their result matches the now decrypted digest
What is a digital certificate and how does it work?
It verifies ownership of a key pair used in asymmetric encryption and can be used to check that a fake key pair isn’t being used by an imposter.
What do digital certificates contain?
They contain: a serial number, the owner’s name, an expiry date, the owner’s public key and the certificate authority’s digital signature.
Name the 3 types of malware
worms, trojans and viruses
What are worms in computing?
Pieces of malicious software that can self-replicate between computers, either within a network or by users downloading and running a malicious file.
What are Trojans in computing?
A type of malware that is disguised as a benign file that users can be tricked into opening. Often spread as email attachments or downloaded from malicious websites.
What are features of viruses in computing?
Require a host file in which to reside
These files are typically executable files
Can lie dormant in a computer until their host file is opened or run
Can spread between computers over a private network , the Internet or even through the use of physical media
What are some ways to prevent malware?
Good code quality, antivirus software, up-to-date software, employee training.
Why can good code quality prevent malware?
Malware often exploit bugs in code that enable them to take hold of a computer system.
How can installing antivirus software prevent malware?
They are specialist pieces of software that scan files on a computer and remove any suspicious files.
How can training employees prevent malware?
They can be trained about the risks of opening suspicious email attachment or other methods in order to reduce the risks posed by malware.
