Describe the types, components and characteristics of computing networks, explain how the internet and the web work and evolved, and evaluate internet dilemmas from privacy to ransomware.
Each is in the Digital Society glossary, with every other term in the subject.
The state of acting or communicating without one's identity being known or traceable by others.
The first large packet-switched computer network, funded by the US Department of Defense and first operating in 1969, which developed many of the technologies on which the internet is built.
The process of checking that a user or device really is who or what it claims to be, using evidence such as a password, a code on a phone or a fingerprint.
The maximum rate at which data can be transferred over a network connection, measured in bits per second (for example, megabits per second).
A network of computers or other connected devices infected with malware and controlled remotely by an attacker, often used for denial-of-service attacks or spam.
A device or program that requests data or services from a server across a network, such as a web browser asking a web server for a page.
A network in which central computers (servers) store data and provide services, and other devices (clients) send requests to them and receive responses.
The delivery of computing resources such as storage, processing and software as a service over a network, from remote data centres, so that users do not need to own or manage the hardware themselves.
Distinguish between types of computing networks: wired, wireless and cloud; PAN, LAN, MAN and WAN; client–server and peer-to-peer.
Describe the role of each component of a network, from network interfaces and switches to routers, modems and transmission media.
Explain how standards, protocols, addresses and domain names allow different devices to work together across the internet.
Outline how identification, authentication, encryption, firewalls, proxy servers, VPNs and security layers protect networks.
Analyse how bandwidth, data compression, net neutrality and the internet backbone shape who can use networks, and how well.
Distinguish between the internet and the world wide web, and describe the roles of URLs, HTTP, browsers and the W3C.
Outline the evolution of the internet and the web, from ARPANET to social media platforms and the Internet of Things.
Evaluate the impacts and implications of internet dilemmas, from privacy and the right to be forgotten to ransomware, for people and communities.
A network is a set of computers and other devices linked so that they can exchange data. The internet is the largest network of all: a global network of networks that carries messages, payments, video calls and medical records between billions of devices, and on which most daily activity in a digital society now depends.
Networks connect to almost every part of the course. The concept of systems explains how millions of independently owned networks behave as one; the concept of power asks who owns the cables, sets the standards and decides what traffic flows; the concept of space describes how networks shrink distance yet leave some places poorly connected. Networks carry the data of 3.1 Data and the content of 3.5 Media, and their effects appear in every context, from telemedicine in 4.4 Health to election interference in 4.6 Political.
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Malicious code that attaches itself to a legitimate program or file and spreads when that file is run or shared, often damaging data or systems.
Malicious software that copies itself and spreads across networks on its own, by exploiting security weaknesses, without needing a user to open a file.
Criminal activity that uses computers or networks, either to attack digital systems directly or to commit traditional crimes such as fraud, theft and extortion.
A part of the deep web that is deliberately hidden and can only be accessed with special software such as Tor, which conceals the identity and location of users and sites.
Encoding data using fewer bits than the original, so that it takes less storage and less time and bandwidth to send.
The parts of the web that search engines do not index, such as private accounts, databases and pages behind logins.
An attack that overwhelms a server, website or network with traffic or requests so that it cannot serve legitimate users; a distributed attack (DDoS) uses many devices at once.
A human-readable name, such as unicef.org, registered by an organisation or person and linked to the IP addresses of its servers.
The distributed system of servers that translates domain names into IP addresses so that devices can find each other on the internet.
Encryption in which data is encrypted on the sender's device and can only be decrypted on the recipient's device, so that no one in between, including the service provider, can read it.
Hardware or software that checks network traffic against a set of security rules and blocks traffic that is not permitted, separating a trusted network from untrusted ones.
Gaining unauthorised access to a computer system, network or data, or using a system in ways its owner did not intend; ethical hacking does the same with permission in order to improve security.
HyperText Transfer Protocol: the protocol that browsers and web servers use to request and send web pages and other resources.
The secure version of HTTP, in which requests and responses between a browser and a web server are encrypted so that they cannot be read or altered in transit.
A simple device that connects devices in a local area network and forwards every incoming message to all other connected devices.
Text displayed on a screen that contains links (hyperlinks) to other text or resources, which the reader can follow directly.
The fraudulent use of another person's personal information, such as their name, identity documents or bank details, to obtain money, goods or services in their name.
The global network of interconnected networks that use the TCP/IP protocols to exchange data between devices.
The very high-capacity fibre-optic links and core routers, owned by major telecommunications companies, that connect the world's large networks and carry most long-distance internet traffic.
A physical location where different networks connect directly to exchange traffic, keeping local traffic local and reducing cost and delay.
The network of everyday physical objects, such as appliances, vehicles, wearables and sensors, that are connected to the internet and collect and exchange data, often without direct human involvement.
An organisation that provides people and organisations with access to the internet, usually for a fee, through fixed or mobile networks.
The ability of different devices, systems and applications, often made by different organisations, to exchange data and use it correctly.
A numerical label that identifies a device on a network using the Internet Protocol, so that packets can be delivered to it; IPv4 addresses are 32 bits long and IPv6 addresses 128 bits.
The time delay between data being sent and being received across a network, usually measured in milliseconds.
A network that connects devices within one building or site, such as a home, school or office, usually owned and managed by one organisation.
Data compression that allows the original data to be rebuilt exactly, used for text, software and files where every detail matters.
Data compression that permanently discards some data, usually detail people barely notice, to make files much smaller, used for photos, music and video.
A network that covers a town or city, connecting LANs across that area, often run by a city authority, university or telecommunications company.
A device that converts digital data into signals suited to a particular transmission line (telephone, cable, fibre or mobile) and back again, connecting a home or office to its internet provider.
The principle that internet service providers must treat all internet traffic equally, without blocking, slowing or charging differently for particular content, applications or websites.
Two or more computers or other devices connected by a transmission medium so that they can share data, resources and services.
The hardware component, now usually built into a device, that connects it to a network through a cable or by radio, and that has a unique hardware (MAC) address.
A small unit of data sent across a network, containing part of a message and a header with the source and destination addresses and a sequence number.
A method of sending data in which a message is split into packets that travel independently, possibly by different routes, and are reassembled at the destination.
A network in which devices share data and resources directly with each other, each acting as both client and server, without depending on a central server.
A network that connects devices around one person over a few metres, such as a phone, a smartwatch and wireless earbuds linked by Bluetooth.
A form of social engineering that uses fake messages or websites imitating trusted organisations to trick people into revealing passwords, financial details or other sensitive information.
An agreed set of rules that defines how data is formatted, transmitted, received and checked when devices communicate.
An intermediary server that forwards requests from users to other servers and returns the responses, so that it can filter, log, speed up or hide traffic.
Malicious software that encrypts a victim's data or locks their systems and demands payment, usually in cryptocurrency, to restore access.
The right of individuals, established in EU law, to ask search engines and organisations to remove links to or delete personal information that is inaccurate, irrelevant, outdated or excessive.
A device that connects two or more networks and forwards data between them, choosing a route for each piece of data based on its destination address.
Manipulating people through deception, for example by pretending to be someone trusted, so that they disclose confidential information or give access to systems.
Websites and apps that let users create, share and respond to content and build networks of contacts, such as Facebook, Instagram, TikTok and WeChat.
Unsolicited messages sent in bulk, usually by email, text or social media, often for advertising, scams or spreading malware.
Malicious software that secretly collects information from a device, such as messages, passwords, location or keystrokes, and sends it to a third party without the user's knowledge.
A published specification agreed by a standards body or industry, such as IEEE 802.11 for Wi-Fi, that manufacturers follow so that their products work together.
A fibre-optic cable laid on the seabed that carries internet and telephone traffic between countries and continents.
A device that connects devices in a local area network and forwards each message only to the device it is addressed to, using MAC addresses.
The family of protocols on which the internet runs; the Internet Protocol (IP) addresses and routes data between networks, and the Transmission Control Protocol (TCP) checks that data arrives complete and in order.
Free software and a volunteer-run network that hides users' identities and locations by sending their traffic through several encrypted relays; it is the most common way to reach the dark web.
The physical path, such as copper cable, fibre-optic cable or radio waves, along which data travels between devices in a network; also called a channel.
Deliberately posting inflammatory, offensive or off-topic content online to provoke, upset or disrupt other users.
A form of authentication that requires two different types of evidence, for example a password (something known) and a code from a phone (something owned).
The integration of computing and network connections into everyday objects and environments so that they are available everywhere and used without conscious attention.
Uniform Resource Locator: the address of a resource on the web, giving the protocol, the server's domain name and the path to the resource.
A service that creates an encrypted connection between a device and a remote server across the internet, so that traffic is hidden from the local network and the user's IP address is hidden from the sites visited.
Technology that carries voice calls as data packets over the internet rather than through the traditional telephone network.
The participatory phase of the web, from the early 2000s, in which users create, share and interact with content on platforms such as blogs, wikis and social networks, rather than only reading published pages.
Software that requests web resources using HTTP or HTTPS and displays them as pages the user can read and interact with.
A service that stores a website's files and applications on servers permanently connected to the internet, so that users can reach the site at any time.
A network that covers a large geographical area such as a country or continent, linking many LANs; the internet is the largest example.
A network in which devices are connected by physical cables, such as copper Ethernet cables or fibre-optic cables.
A network in which devices exchange data through the air using radio waves, as in Wi-Fi, Bluetooth and mobile phone networks.
A system of linked documents and applications, identified by URLs and transferred using HTTP, that runs on the internet and is accessed through web browsers.
An international organisation that develops open, royalty-free standards for the web, such as HTML and accessibility guidelines, so that the web works for everyone on any device.
The practice by which a mobile or internet provider lets customers use particular apps or websites without the data counting towards their paid allowance.
Networks let data and information be created, accessed and shared in a distributed way. Instead of one machine holding everything, data sits on many devices in many places, and the network moves it to wherever it is needed. A student in Lagos can edit a document stored on a server in Ireland while a classmate in Jakarta comments on it, without either knowing where the file physically is.
Networks are also layered: a home network connects to a provider's network, which connects to national and international networks, each run by a different organisation. The internet therefore has no single owner and no single off switch.
Networks are classified in three ways: by the medium that carries data (wired, wireless, or reached as a cloud service), by scale (PAN, LAN, MAN, WAN) and by architecture, meaning how devices relate to each other (client–server or peer-to-peer). One network belongs to all three classifications at once: a school's network is typically a wired and wireless LAN with a client–server architecture.
A wired network uses copper cables (electrical signals) or fibre-optic cables (pulses of light), which reach far higher speeds over longer distances. A wireless network uses Wi-Fi inside buildings, Bluetooth around one person, 4G and 5G mobile networks across countries, and satellites over oceans and remote regions.
Feature | Wired | Wireless |
|---|---|---|
Speed and reliability | Usually faster and more stable | Slower; walls, distance and crowding reduce quality |
Mobility | Devices stay where the cable reaches | Devices move freely within range |
Security | Interception needs physical access | Signals spread through the air, so encryption is essential |
Cost of reaching new users | High: cables must be laid | Lower: one mast or satellite serves a wide area |
Typical use | Data centres, offices, the internet backbone | Homes, phones, rural and mobile access |
Wireless technology changed who could get online. In much of sub-Saharan Africa and South Asia, most people first used the internet on a mobile phone rather than a fixed line, because a mast is far cheaper than a cable to every house. Coverage is still uneven, as the 5G chart shows: the newest wireless networks reach most people in Europe and the Americas but only about one person in nine in Africa. Through the concept of space, wireless networks reduce the importance of distance but also reproduce inequalities between regions, part of the digital divide.
Cloud computing means using storage, processing power and software provided over the internet from large data centres owned by someone else. Saving photos to iCloud, writing in Google Docs or watching Netflix all use the cloud: the data and the programs that handle it sit on servers in a provider's data centre, not on the user's device. The largest providers, such as Amazon Web Services, Microsoft Azure and Google Cloud, rent out storage, computing power and ready-made software.
A start-up in Nairobi can rent the same computing power as a multinational for a few dollars an hour, which lowers the barrier to starting a digital business (4.2 Economic). The same arrangement concentrates data and power in a handful of providers: when one suffers an outage, thousands of unrelated services fail together, and data about a country's citizens may be stored abroad under another country's laws.
Networks are also named by the area they cover. The four scales nest inside each other, as the scale diagram shows.
Type | Typical range | Typical owner | Example |
|---|---|---|---|
Personal area network (PAN) | A few metres | One person | Phone, smartwatch and earbuds over Bluetooth |
Local area network (LAN) | One building or site | A household, school or business | A school's wired and Wi-Fi network |
Metropolitan area network (MAN) | A town or city | City authority, university or telecom company | A city's fibre network linking schools, libraries and council offices |
Wide area network (WAN) | Country, continent, world | Telecom companies, large organisations | A bank's international network; the internet |
The third classification looks at how devices relate to each other, as the architecture diagram contrasts. In a client–server network, servers provide data and services and clients request them: when a student opens Instagram, the app is a client asking Meta's servers for posts. In a peer-to-peer network (P2P), there is no central server, and every device, or peer, can both request and supply data.
Most familiar services, such as email, websites, online banking and school learning platforms, are client–server. The design suits organisations that need control, because the server owner decides who may log in, keeps the authoritative copy of the data and applies updates in one place. Its weakness is concentration: if the server fails or is attacked, every client loses the service.
Peer-to-peer networks spread the work across many devices. BitTorrent splits large files into pieces that users download from, and upload to, each other, so the more people share a file the faster it spreads. Bitcoin also runs on a P2P network in which every computer holds a copy of the blockchain ledger. Without a centre, P2P networks are hard to shut down, which helps activists but frustrates rights holders trying to stop piracy.
Client–server | Peer-to-peer | |
|---|---|---|
Control | Central: one owner sets rules and security | Shared: no single owner |
Resilience | Server failure stops the service | Survives the loss of many peers |
Scaling | More users need more server capacity | More users add more capacity |
Security | Easier to secure, monitor and back up | Harder to secure; shared files may carry malware |
Examples | Email, websites, online banking, cloud storage | BitTorrent, Bitcoin |
Every network, from home Wi-Fi to the internet backbone, is built from the same kinds of parts: devices (clients, servers, hubs, switches, routers, modems), parts of devices (network interfaces) and the paths that data travels along (channels). The home network diagram shows how they fit together.
Client and server are roles rather than types of machine: an ordinary laptop can act as a server for a game played by friends. To join any network, a device needs a network interface: the hardware that connects it to the transmission medium. In older desktop computers this was a separate network interface card (NIC); today it is usually built in. Each has a unique hardware address, the MAC address.
Inside a LAN, devices meet at a central connecting point. A hub copies every message it receives to every other port, so each device sees all traffic, which wastes capacity and lets any connected device read others' messages. A switch learns the MAC address on each port and sends each message only to its intended device.
A router connects different networks and forwards data between them. It reads the destination address on each piece of data and sends it one network closer to that address. A modem (modulator–demodulator) converts digital data into the kind of signal the line to the provider can carry, and back again. The type depends on the line: DSL for telephone lines, cable modems, optical terminals for fibre, or mobile modems.
The path data travels along is a channel, or transmission medium.
Medium | How data travels | Strengths | Weaknesses |
|---|---|---|---|
Copper cable | Electrical signals | Cheap; already in many buildings | Signal weakens over distance; interference |
Fibre-optic cable | Pulses of light in glass | Very high capacity over long distances | Expensive to lay |
Radio (Wi-Fi, Bluetooth, 4G/5G) | Electromagnetic waves | Mobility; quick to deploy | Limited range; easier to intercept |
Satellite | Radio signals to and from orbit | Reaches ships and remote areas | Delay for distant orbits; weather; cost |
The choice of medium has social consequences. Fibre gives fast, reliable connections but costs most where people are fewest, so rural areas are often connected last.
Billions of devices from thousands of manufacturers exchange data every second because they follow shared rules. A protocol is a set of rules for how data is formatted, sent, received and checked. A standard is a published, agreed specification that any manufacturer can follow: Wi-Fi follows the IEEE 802.11 family of standards and wired Ethernet follows IEEE 802.3, so a laptop from one country works with a router from another.
Interoperability is the main purpose of standards. Because email follows open protocols, a Gmail user can write to someone using Outlook; because the web follows open standards, any browser opens any website.
Interoperability is also a matter of power. A WhatsApp user cannot message a Telegram user, which keeps people on the platform where their contacts already are. The EU's Digital Markets Act (2022) requires the largest messaging services to open up to smaller rivals, trading some security risk for competition and choice.
The internet runs on a family of protocols called TCP/IP. The Internet Protocol (IP) gives every device an address and moves data between networks; the Transmission Control Protocol (TCP) makes sure data arrives complete and in order. The family is organised in layers, from protocols for particular services such as HTTP and email at the top to Ethernet and Wi-Fi, which move data across one physical link, at the bottom.
Data crosses the internet in small units called packets, each carrying a piece of the data plus a header with the source address, destination address and a sequence number. In packet switching, routers forward every packet independently along whatever route is best at that moment, so packets from one message may take different paths and arrive out of order. The receiver reassembles them, and any packet that goes missing is sent again, as the packet-switching diagram shows.
Packet switching makes the internet efficient, because many users share the same links at once instead of reserving a whole line for one conversation, as the old telephone network did. It also makes it resilient, because routers can send packets around a broken link. The idea came from 1960s research into networks that could survive damage.
YouTubeAn IP address is a numerical label that identifies each device on an IP network so that packets can find it. IPv4 uses 32-bit addresses such as 142.250.180.14, giving about 4.3 billion possible addresses, far fewer than the devices now online; the bodies that allocate them have largely run out. IPv6 uses 128-bit addresses such as 2001:db8::1, giving about 3.4 × 10³⁸. A device's MAC address is set in its hardware, although many phones now show each Wi-Fi network a random one for privacy; its IP address changes whenever it joins a different network.
IP addresses suit machines, not people. A domain name such as who.int or bbc.co.uk is a human-readable name linked to a server's IP addresses, read from right to left: top-level domain (.int, .uk), registered name, then subdomains (www). The Domain Name System (DNS) translates names into addresses. A device asks a DNS resolver, usually run by its internet provider; if the resolver does not know the answer, it asks the root servers, then the servers for the top-level domain, then the organisation's own server, and stores the answer for next time.
DNS is also a point of control. Governments and internet providers can block a website by telling DNS resolvers not to answer for its name, which is how many countries enforce court orders against piracy sites or censor political content.
Network security protects the confidentiality of data (only the right people can read it), its integrity (it is not changed without permission) and its availability (it can be reached when needed). The main tools are identification and authentication, encryption, firewalls, proxy servers and VPNs, arranged in layers.
Identification is the claim of who a user or device is, such as entering a username. Authentication is the check that the claim is true, using one or more factors:
something the user knows: a password or PIN;
something the user has: a phone receiving a code, a bank card or a security key;
something the user is: a fingerprint or face (biometrics).
Two-factor authentication (2FA) requires two different factors, so a stolen password alone no longer opens an account. Passkeys, which keep a secret key on the user's device and unlock it with a fingerprint or face, are replacing passwords on major platforms.
Encryption scrambles data with a mathematical key so that only someone with the right key can read it. On networks it protects data in transit: anyone intercepting packets on public Wi-Fi or a backbone cable sees only meaningless characters. Most web traffic now uses HTTPS, shown by the padlock in the browser. WhatsApp and Signal use end-to-end encryption, so not even the company running the service can read messages. Public-key cryptography lets strangers, such as a shopper and an online shop, set up a secure connection: anyone can encrypt with the shop's public key, but only its private key decrypts.
Strong encryption creates a dilemma of values. It protects journalists, dissidents and ordinary users from criminals and surveillance, but also stops police reading suspects' messages even with a warrant. Governments in the UK and the EU have proposed ways to access or scan encrypted messages; security experts reply that a "back door" built for the police can also be found by criminals and hostile states.
A firewall checks traffic entering and leaving a network or device against rules and blocks what is not allowed, for example permitting visits to a company's public website while blocking outside attempts to reach its internal file servers. A proxy server sits between users and the internet and passes requests on for them, so websites see the proxy's IP address rather than the user's; schools use proxies to filter and log web access and to cache popular pages. A virtual private network (VPN) creates an encrypted "tunnel" between a device and a VPN server, hiding traffic from the local network and the internet provider and hiding the user's IP address from the sites visited.
VPNs serve very different stakeholders: employees reach company systems from home, activists in countries that block websites reach independent news, and governments that block foreign platforms restrict VPNs as a threat to their laws. A VPN also moves trust rather than removing it: the VPN provider can see the traffic the internet provider no longer can, and some free VPN apps have been found selling users' data.
No single tool is enough, so organisations arrange security in layers, an approach called defence in depth. An attacker who gets through one layer, for example by guessing a password, should be stopped by another, such as 2FA, an up-to-date device or encrypted data. The security layers diagram runs from people and policies on the outside to the data at the centre.
The outermost layer is human: many attacks start with a person being tricked or an update being missed. The WannaCry attack of 2017 shows what happens when one layer is missing across a large organisation.
A network's capacity is how much data it can carry and how quickly. It decides whether a family can stream a lesson, a hospital can send scans, or a rural business can sell online.
Bandwidth is the maximum amount of data a connection can carry per second, measured in megabits (Mbps) or gigabits (Gbps) per second. Latency is the delay between sending data and its arrival, in milliseconds; it depends on distance, the medium and the number of routers on the way. High bandwidth matters for downloads and streaming, low latency for video calls, online games and remote control of machines.
Data compression reduces the number of bits needed to store or send data. Lossless compression removes repetition in a way that can be reversed exactly; ZIP files and PNG images use it, and it suits text, software and medical images. Lossy compression permanently discards detail people are unlikely to notice; JPEG photos, MP3 music and streaming video use it, making files many times smaller.
Compression widens access. Streaming services lower video quality automatically on slow connections, so a student on a weak mobile signal can still watch a lesson. During the first COVID-19 lockdowns in March 2020, Netflix and YouTube reduced their default video quality in Europe at the European Commission's request, to ease pressure on networks as millions began working and studying from home.
Net neutrality is the principle that internet service providers should treat all data equally, without blocking, slowing or charging extra for particular sites, apps or content. Without it, a provider could slow a rival's video service or sell a "fast lane" that small sites and non-profit organisations cannot afford. A related practice, zero-rating, lets customers use certain apps without the data counting against their allowance: supporters say it gives people on low incomes free access to useful services; critics say it steers new users towards platforms that partner with the provider.
Place | Decision | Claim behind it |
|---|---|---|
European Union | A 2015 regulation requires providers to treat traffic equally, except to manage congestion | Protect competition and users' choice |
India | In 2016 the regulator TRAI banned different prices for different content, ending Facebook's zero-rated Free Basics there | A free but limited "internet" chosen by one company is not genuine internet access |
United States | Rules adopted in 2015, repealed in 2017, restored in 2024 and struck down by a federal appeals court in January 2025 | Opponents: rules discourage investment in networks. Supporters: providers hold too much power over what users see |
The internet backbone is the set of very high-capacity links, mostly fibre-optic, and core routers that join the world's major networks, owned by large telecommunications companies that agree to carry each other's traffic. Networks also meet at internet exchange points (IXPs), where many providers connect directly so local traffic stays local.
Across oceans, the backbone runs through more than 500 submarine cables laid on the seabed, which carry almost all data between continents; satellites carry only a small share.
This physical layer makes the internet more fragile than it seems, especially for small island states that depend on a single cable. In early 2024 three cables in the Red Sea were damaged, apparently by the dragging anchor of a ship disabled in an attack, and operators had to reroute traffic between Asia, the Middle East and Europe.
Ownership is changing too. Large platform companies now fund or co-own many new cables; Meta led the consortium behind 2Africa, a cable of about 45,000 km around Africa. Through the concept of power, this gives a few technology companies influence over the infrastructure as well as the services of the internet. Through the concept of space, cable routes decide which coastal cities become digital hubs.
An internet service provider (ISP) gives homes, schools and businesses access to the internet through fibre, cable, DSL or mobile networks, assigns IP addresses, runs DNS resolvers and passes traffic onto the backbone. ISPs range from global telecommunications companies to local cooperatives and mobile operators such as Safaricom in Kenya.
Every byte a customer sends passes through the ISP, which gives it power: it can see which domains a customer visits unless traffic is encrypted, and governments can order it to block sites or cut connections. Its prices also shape access: when Reliance Jio entered India's mobile market in 2016 with free introductory data and then very low prices, rivals cut prices too, and India's mobile data became some of the cheapest in the world.
Each service uses its own protocols on top of TCP/IP.
Service | What it does | Real-world example |
|---|---|---|
Messages delivered between mail servers using open protocols (SMTP) | Gmail, Outlook, school email | |
Chat and online messaging | Real-time text, images and voice notes between people and groups over the internet | WhatsApp, WeChat, Telegram, Discord |
Texting | Short messages over the mobile phone network (SMS), which work without internet access | Bank and government SMS alerts |
File sharing | Sending or synchronising files, through cloud storage or P2P | Google Drive, Dropbox, BitTorrent |
VoIP | Voice calls carried as packets over the internet | WhatsApp calls, Microsoft Teams calls |
Hosting | Renting space on servers so a website or app is always online | A small business site on a hosting company's servers |
Video conferencing | Live video meetings between several participants | Zoom, Google Meet, Teams |
VoIP and messaging cut the cost of international calls to almost nothing, which matters greatly to migrant workers keeping in touch with families abroad (4.7 Social). Video conferencing let schools, courts and doctors keep working during COVID-19 lockdowns, while pupils without a reliable connection fell further behind (4.5 Human knowledge). Messages forwarded inside private, encrypted groups are hard to fact-check, which has made messaging apps channels for election rumours (4.6 Political).
The internet and the World Wide Web are different systems. The internet is the network of networks: the cables, routers and protocols that move packets. The web is one service that runs on it: linked pages and applications reached through a browser. Email, VoIP calls, online games and BitTorrent use the internet without using the web. The web is built on hypertext, text containing links that take the reader directly to other documents; pages are written in HTML (HyperText Markup Language), and the links between them, not any single site, make the web a "web".
Three elements work together every time a page loads.
Element | What it is | Role |
|---|---|---|
URL | The address of a resource, such as | Names the protocol ( |
HTTP | The request–response protocol of the web | The browser sends a request; the server replies with a status code ( |
Web browser | Software such as Chrome, Safari, Edge or Firefox | Sends requests and turns HTML, images, styles and scripts into the page on screen |
HTTPS is HTTP sent through an encrypted connection, so passwords, card details and the pages visited cannot be read in transit.
The World Wide Web Consortium (W3C), founded by Tim Berners-Lee in 1994, develops open, royalty-free web standards, including HTML, CSS (the visual style of pages) and the Web Content Accessibility Guidelines (WCAG) for making sites usable by people with disabilities. Its members include universities, companies, governments and non-profit organisations, and since 2023 it has been an independent public-interest non-profit organisation.
Open standards spread power: a developer in Dhaka can build a site that works in every browser without paying anyone. The W3C cannot enforce its standards, however. Browser makers decide which features to support, and since most browsers now run on Google's Chromium engine, one company's decisions strongly shape the web in practice.
The history of networks shows the interaction of military funding, university research, individual innovators and, later, commercial companies.
In the early 1960s Paul Baran at the RAND Corporation in the United States and, independently in the mid-1960s, Donald Davies at the UK's National Physical Laboratory proposed breaking messages into blocks sent through a decentralised network; Davies called them "packets". The US Department of Defense's Advanced Research Projects Agency funded ARPANET, which sent its first message from the University of California, Los Angeles to the Stanford Research Institute on 29 October 1969.
Year | Innovation | Innovators | Why it mattered |
|---|---|---|---|
1960s | Packet switching | Paul Baran, Donald Davies | Efficient, resilient sharing of networks |
1969 | ARPANET's first link | ARPA, UCLA, Stanford Research Institute | First working wide-area packet-switched network |
1971 | Network email using @ | Ray Tomlinson | First widely used network application |
1974 | TCP design published (later split into TCP and IP) | Vint Cerf, Bob Kahn | Common language for interconnecting networks |
1983 | ARPANET adopts TCP/IP; DNS designed | Paul Mockapetris (DNS) | The "network of networks"; readable names |
1989–1991 | World Wide Web created at CERN | Tim Berners-Lee, with Robert Cailliau | URLs, HTTP and HTML made information easy to link |
1993 | Web software released free; Mosaic browser | CERN; Marc Andreessen, Eric Bina | Free, graphical web spreads to the public |
1990s | Commercial ISPs and e-commerce | Many companies | The internet moves into everyday life |
Berners-Lee proposed his information system at CERN, the European physics laboratory near Geneva, in March 1989, to help scientists share documents across incompatible computers. He wrote the first browser and the first web server, which ran on the NeXT computer in the photograph. CERN's decision in April 1993 to make the web software freely available, rather than charge licence fees, is a major reason the web grew so quickly.
Through the concept of change, these developments show both continuity and discontinuity. The internet grew out of existing telephone lines and Cold War research priorities, yet open protocols and free software allowed uses their designers never planned, from online shopping to global social movements.
The early web was mostly read-only: organisations published pages and visitors read them. From the early 2000s, Web 2.0 described a participatory web in which ordinary users create and share content through blogs, wikis, video and social networks; the publisher Tim O'Reilly popularised the term from 2004. Social media platforms grew from this model: early networks such as Friendster (2002) and MySpace (2003) gave way to Facebook (2004), YouTube (2005), Twitter (2006), WeChat (2011) and TikTok (international launch 2017).
Smartphones moved social media into people's pockets, and recommendation algorithms (3.2 Algorithms) turned feeds from lists of friends' posts into streams selected to hold attention. Social media changed how people express identity (2.3), organise politically (4.6) and run businesses (4.2), and it concentrated much of the world's communication on a few privately owned platforms whose design and moderation rules affect billions of users.
YouTubeThe Internet of Things (IoT) is the network of physical objects with sensors, software and network connections that exchange data without direct human input: smart thermostats, fitness trackers, connected cars, factory machines and smart electricity meters. Kevin Ashton is credited with the term (1999). Ubiquitous computing, or ubiquitous networking, is the idea that computing becomes so embedded in surroundings that people stop noticing it; Mark Weiser of Xerox PARC described it in 1991, and smartphones, voice assistants and contactless payment make much of it real.
The IoT brings opportunities: smart meters help households cut energy use (4.3 Environmental) and remote monitoring lets older patients live at home for longer (4.4 Health). It also multiplies dilemmas. Devices collect data about the people around them, often with unclear consent, and many cheap devices ship with weak default passwords and never receive updates, which makes them easy to capture, as the Mirai attack of 2016 showed.
The internet's openness, reach and speed create dilemmas: situations in which important values, or the interests of different people and communities, conflict. Some concern personal information; others concern harmful and criminal activity.
Online privacy is people's ability to control what information about them is collected, who sees it and how it is used (data privacy is covered in 3.1 Data). Every network action leaves traces: IP addresses in server logs, DNS queries, cookies, phone location data and the metadata of messages (who contacted whom, when and from where).
Anonymity protects whistle-blowers, abuse survivors, sexual minorities in hostile countries and political dissidents. It also shields trolls and fraudsters from consequences. Complete anonymity is rare, because IP addresses, payment details and behaviour patterns can often be linked back to individuals.
Surveillance, the systematic monitoring of people's activities, is carried out online by states (for security and law enforcement), by companies (to target advertising) and by individuals (parents, partners, employers). In 2013 documents leaked by Edward Snowden showed that the US National Security Agency and the UK's GCHQ were collecting very large volumes of internet and phone data, including by tapping backbone cables and obtaining data from major technology companies. Governments argued that bulk collection was needed to stop terrorism; technology companies responded by encrypting far more traffic. Civil liberties groups claim that mass surveillance treats everyone as a suspect and discourages free expression.
The right to be forgotten was established in EU law by the 2014 judgment of the Court of Justice of the European Union in Google Spain v AEPD and Mario Costeja González. Costeja objected that a Google search for his name still showed 1998 newspaper notices about the forced sale of his property to pay social security debts, long after the debts were settled. The court ruled that search engines must, on request, remove links to information that is inadequate, irrelevant or no longer relevant, unless the public interest outweighs the person's privacy. The newspaper archive stayed online; only the link from searches of his name went.
The right became the "right to erasure" in the EU's General Data Protection Regulation (2018). In 2019 the same court ruled that Google need only remove links from its European search results, not worldwide, which shows how a right defined in one region meets the global reach of the internet. Individuals claim that people change and old misfortunes should not define them forever; search engines object to acting as judges of the public interest; journalists and historians warn that removing links can hide information the public needs.
Spyware is malware that secretly collects information from a device, such as keystrokes, messages, location or camera images, and sends it to someone else. It ranges from "stalkerware" secretly installed on a partner's or child's phone, which lets one person track another's messages and location, to commercial tools that governments buy to monitor targets.
Identity theft is the use of someone else's personal information to commit fraud, such as opening accounts or taking out loans in their name. Stolen data comes from breaches, phishing and spyware. In September 2022 a breach at Optus, one of Australia's largest telecommunications companies, exposed personal details of up to about 10 million current and former customers, including many passport and driving licence numbers; governments replaced documents and banks added checks to reduce the risk of identity theft.
Cybercrime includes crimes that target computer systems (hacking, malware, denial of service) and traditional crimes made easier by networks (fraud, extortion, sale of illegal goods). It is international by nature: an attacker in one country can target victims in dozens of others, while police powers stop at borders. The Council of Europe's Budapest Convention (2001) was the first international treaty on cybercrime, and the UN General Assembly adopted a global cybercrime convention in December 2024. Losses reported to the FBI's Internet Crime Complaint Center, shown in the cybercrime chart, give a sense of scale, although they cover only crimes that victims report, mainly in the United States.
Hacking is gaining unauthorised access to systems or data. Black hat hackers break in for profit, damage or espionage; white hat (ethical) hackers test systems with the owner's permission, often paid through "bug bounty" programmes; grey hat hackers break in without permission but without criminal intent, sometimes to expose flaws. Through the concept of values and ethics, the same skill is harmful or protective depending on consent and purpose, which is why many laws focus on authorisation rather than technique.
Malware (3.3 Computers) spreads in different ways. A computer virus attaches itself to a file and spreads when the file is opened and shared; a worm spreads across networks by itself, without any user action. In May 2000 the ILOVEYOU malware, created in the Philippines, arrived as an email "love letter"; when opened, it overwrote files and mailed itself to every contact, reaching millions of computers within days.
Ransomware encrypts a victim's files or locks their systems and demands payment, usually in cryptocurrency, for the key; many gangs now also steal data and threaten to publish it. In May 2021 a ransomware attack led Colonial Pipeline to shut down the largest fuel pipeline on the US East Coast for several days, causing fuel shortages, and the company paid a ransom of several million dollars. Paying restores some victims' systems quickly but funds criminal groups and encourages further attacks, which is why many governments advise against it.
Spam is unsolicited bulk messaging by email, text or social media. It wastes time and network capacity and delivers many scams and malware, although filters now block most of it. Social engineering manipulates people, rather than technology, into giving away information or access, exploiting trust, fear and urgency. Its most common form is phishing: fake emails, texts or websites that copy a trusted organisation to collect passwords or payment details. In July 2020 attackers phoned Twitter employees pretending to be from the company's IT department, obtained logins to internal tools and took over accounts including those of Barack Obama and Elon Musk to post a cryptocurrency scam, without exploiting any technical flaw.
A denial-of-service attack (DoS) floods a server or network with traffic so that it cannot serve genuine users. A distributed attack (DDoS) uses thousands or millions of devices at once, usually a botnet of machines infected with malware and controlled remotely. On 21 October 2016 the Mirai botnet, built largely from hijacked IoT devices such as security cameras that still used factory-default passwords, attacked Dyn, a DNS provider. Because DNS could not answer, users across North America and Europe could not reach Twitter, Netflix, Reddit and GitHub for hours, although those services' own servers were working.
The deep web is all web content that search engines do not index: email inboxes, online banking, school learning platforms and subscription databases. It is far larger than the visible web and almost entirely ordinary. The dark web is a small part of it reachable only with special software, most commonly Tor, which hides users' locations by passing traffic through several encrypted relays run by volunteers. It hosts illegal markets for drugs, stolen data and malware, such as Silk Road, shut down by the FBI in 2013. It also protects legitimate users: the BBC launched a dark-web version of its news site in 2019 for readers in countries that block it.
Trolling is deliberately posting provocative or offensive content to upset people or start arguments. It ranges from provocation in comment sections to coordinated harassment of individuals, often women, minorities and public figures, and overlaps with cyberbullying (4.7 Social). Anonymity and scale make trolling cheap for the troll and costly for the target, who may withdraw from public debate. Responses include moderation, blocking tools and law: Australia's Online Safety Act 2021 lets the eSafety Commissioner order platforms to remove serious online abuse of adults.
On Friday 12 May 2017 a ransomware program called WannaCry spread around the world within hours. Europol estimated that it hit more than 200,000 computers in about 150 countries, from Renault factories in France to Deutsche Bahn in Germany. Its best-known victim was the National Health Service (NHS) in England, which provides free public health care through hundreds of separate trusts, hospitals and GP (family doctor) practices, each responsible for its own IT.
WannaCry combined ransomware with a worm, so it spread without anyone clicking a link. The attack chain diagram shows the cycle.
Entry. Infected computers scanned the internet and local networks for machines accepting connections through SMB, a Windows protocol for sharing files and printers.
Exploit. WannaCry used EternalBlue, a tool for exploiting a flaw in an old version of SMB. It had been developed by the US National Security Agency and leaked online by a group called the Shadow Brokers in April 2017. Microsoft had released a patch in March 2017, but many organisations had not installed it, and Windows XP no longer received regular updates.
Encryption. WannaCry encrypted documents, images and databases and demanded $300 in Bitcoin, rising to $600 after three days.
Spread. Each infected computer scanned its own network for more targets. Many organisations' networks were "flat", with few internal barriers, so one infection could reach many machines.
The attack slowed sharply that afternoon. A British security researcher, Marcus Hutchins, noticed that the malware tried to contact an unregistered web domain before running; he registered it for about $11, and new infections that reached it stopped. In December 2017 the US and UK governments attributed WannaCry to the Lazarus Group, a hacking group linked to the North Korean state.
Measure | Figure |
|---|---|
NHS trusts in England affected (infected, or disrupted while protecting themselves) | At least 81 of 236 (about a third) |
GP practices infected | 595 (603 primary care and other NHS organisations in total) |
Appointments and operations recorded as cancelled | 6,912 (NHS England estimated over 19,000 in total) |
Hospital A&E departments that diverted patients elsewhere | 5 |
Ransom paid by any NHS organisation | None |
Estimated cost to the NHS | £92 million: £19 million lost output, £73 million IT costs |
Source: National Audit Office, Investigation: WannaCry cyber attack and the NHS, 2017; Department of Health and Social Care, Securing cyber resilience in health and care, 2018.
Patients had operations and appointments cancelled, and some emergency patients were taken to more distant hospitals. Without access to test results, scans or records, care slowed. NHS organisations reported no cases of harm to patients or of data being stolen, although the full extent of disruption was never known.
Staff returned to pen and paper, phoned results between departments and worked long hours through the weekend. Because the attack began on a Friday, most GP practices had the weekend to recover.
The public learned that a health service could be disrupted by malware built from a national intelligence agency's tool, raising questions about trust in public bodies and the security of digital health systems.
Systems. The NHS is a large system of interdependent elements: computers, medical devices running Windows, shared networks, staff and patients. Flat networks let the worm move freely inside trusts, and some equipment, such as scanners, ran Windows versions that could not be updated without the manufacturer's approval. Failure came not from one mistake but from gaps in several security layers at once: unpatched devices, weak internal separation of networks, and limited central authority and training.
Power. The NSA had found the SMB flaw and kept it secret for intelligence use rather than telling Microsoft. Microsoft's president Brad Smith argued afterwards that governments stockpiling vulnerabilities put everyone at risk, comparing the leak to the theft of military missiles. Patients, the least powerful stakeholders, had no part in any of these decisions but bore their effects. Within the NHS, power was spread across hundreds of trusts, so no one could require all of them to patch quickly.
Values and ethics. Cyber security competes in a public health budget with doctors and medicines, so delaying the replacement of old systems is also an ethical choice about risk to patients.
The National Audit Office concluded that the attack could have been prevented by basic IT security practice. Trusts had been warned in 2014 to move off Windows XP, and NHS Digital issued critical alerts about the flaw in March and April 2017, but cyber security was not a priority in most trusts and there was no tested national response plan. Afterwards the government announced £150 million over three years for NHS cyber security, agreed a national deal with Microsoft to move NHS computers to Windows 10, and set up a security operations centre to monitor threats.
These responses strengthened the device and policy layers that WannaCry exploited, but not the underlying tension between a connected health system that shares data to improve care and the security of that system. In June 2024 a ransomware attack on Synnovis, a pathology company serving several London hospitals, again forced the postponement of thousands of appointments and procedures and led to patient data being published. The NHS was better protected against WannaCry's specific weakness, but not against attacks that exploit suppliers and human error.
WannaCry shows that network connection lets damage spread at network speed, that security depends as much on organisation, funding and governance as on technology, and that decisions by powerful actors far from the hospital can fall hardest on patients who had no part in them.
Why it earns the marks: (b) answers follow a chain of cause, mechanism and effect for three marks each. The (c) response reaches the 7–8 band because it uses a named real-world example, analyses impacts on specific groups through the concept of power, and reaches a conditional judgement rather than a list of advantages and disadvantages.
Why it earns the marks: it uses the source explicitly, adds an accurate real-world example and explains two distinct reasons, as a 4-mark AO2 question expects.
I can distinguish between wired, wireless and cloud networks, with an advantage and a disadvantage of each.
I can describe PAN, LAN, MAN and WAN with an example of each.
I can distinguish between client–server and peer-to-peer networks, including their effects on control and resilience.
I can describe the role of a client, server, network interface, hub, switch, router, modem and transmission medium.
I can explain how protocols and standards make interoperability possible, and how TCP/IP and packet switching work.
I can distinguish between an IP address, a MAC address and a domain name, and explain what DNS does.
I can outline how identification, authentication, encryption, firewalls, proxy servers and VPNs protect networks, and why security is arranged in layers.
I can explain bandwidth, latency and lossy and lossless compression, and evaluate net neutrality with real decisions from different countries.
I can describe the internet backbone, submarine cables, ISPs and the main network services, and analyse why infrastructure makes some places vulnerable.
I can distinguish between the internet and the web, and describe the roles of URLs, HTTP, browsers and the W3C.
I can outline key innovators and innovations in the early internet and web, the rise of social media and the Internet of Things.
I can explain each internet dilemma, from privacy and the right to be forgotten to ransomware, the dark web and trolling, with a real example.
I can analyse the WannaCry attack on the NHS through at least two concepts and evaluate the response.