The internet and the world wide web

Although often used interchangeably, the internet and the World Wide Web (WWW) are two distinct concepts. The internet is the physical infrastructure – a massive, global network of interconnected computers, servers, routers, and cables. Think of it as the roads and motorways. It's a Wide Area Network (WAN) that allows devices all over the world to connect and communicate with each other. The World Wide Web, on the other hand, is the collection of information, websites, and web pages that is accessed using the internet. The Web is a service that runs on the internet. If the internet is the road system, the Web is all the shops, houses, and destinations you can visit by travelling on those roads.

Accessing a web page involves a seamless, multi-step process. It starts when you type a Uniform Resource Locator (URL) into your web browser. A URL is a unique, text-based address for a web page. It has three parts: the protocol (e.g., 'https'), the domain name (e.g., 'www.cambridge.org'), and the file path/name (e.g., '/education/').

1. The browser sends the domain name to a Domain Name Server (DNS). The DNS is like the internet's phonebook; it looks up the human-friendly domain name to find the corresponding machine-readable IP address (e.g., 192.0.2.146).
2. The DNS returns the IP address to the browser.
3. The browser then sends a request to the web server located at that IP address. This request uses a specific protocol, which is a set of rules for communication. The most common are HTTP (Hypertext Transfer Protocol) and HTTPS (Hypertext Transfer Protocol Secure). HTTPS is the secure version; it encrypts the data between your browser and the server, making it unreadable to anyone who might intercept it.
4. The web server receives the request, finds the requested web page files (written in languages like HTML and CSS), and sends them back to your browser.
5. Finally, your browser receives the files and renders them, displaying the web page on your screen.

A web browser is a software application whose primary purpose is to retrieve web page files (like HTML, CSS, and JavaScript) from a web server and render them into a visual, interactive page for the user. However, modern browsers have many other functions, including:

• Keeping a history of visited websites.
• Storing bookmarks or favourites for quick access.
• Managing downloads.
• Caching data to load previously visited pages faster.
• Storing cookies.

A cookie is a small text file that a website stores on your computer. Its purpose is to remember information about you. This could be your login status, items in your shopping cart, or your preferences (like language or theme). There are two main types:

• Session Cookies: These are temporary and are stored only for the duration of your browsing session. They are deleted automatically when you close your browser. They are perfect for tasks like keeping you logged in or managing a shopping cart as you move from page to page.
• Persistent Cookies: These are stored on your computer for a longer period and have an expiry date. They remain even after you close your browser. They are used to remember your preferences and login details between visits, and also for tracking your browsing habits across different websites for advertising purposes.

A digital currency is any currency that exists only in digital or electronic form, not in physical form like banknotes or coins. While this includes money in your bank account, the term is now commonly associated with cryptocurrency.

A cryptocurrency (e.g., Bitcoin, Ethereum) is a decentralised digital currency secured by cryptography. 'Decentralised' means it is not controlled by any single entity like a government or central bank. This is made possible by a technology called blockchain.

Blockchain is a distributed, immutable digital ledger. Let's break that down:

• Ledger: It's a record book of all transactions.
• Digital: The ledger is a computer file.
• Distributed: Instead of one person or company holding the ledger, an identical copy is held by thousands of computers across the network. This makes it highly resilient and transparent.
• Immutable: Transactions are grouped into 'blocks'. Each new block is cryptographically linked to the previous one, forming a 'chain'. Once a block is added to the chain, it is extremely difficult to alter or delete it without the rest of the network noticing. This makes the transaction history secure and trustworthy.

Cyber security threats are malicious acts that seek to damage data, steal data, or disrupt digital life. Key threats include:

• Malware: Short for 'malicious software', this is a broad term for any software designed to cause harm. Examples include viruses, worms, spyware, and ransomware.
• Phishing: A fraudulent attempt to trick a user into revealing sensitive information (like passwords or credit card details) by disguising as a trustworthy entity in an email or message.
• Pharming: A more technical attack where a user is redirected to a fraudulent website without their knowledge, even if they type the correct URL. This is often done by compromising a DNS server.
• Brute-force Attack: An attempt to crack a password or username by trial and error, systematically trying every possible combination.
• Data Interception: The act of illegally listening to or stealing data as it is transmitted over a network. This is why unencrypted Wi-Fi is risky.
• Social Engineering: The art of manipulating people into giving up confidential information. Phishing is a type of social engineering, but it can also happen via phone calls or in person.
• Hacking: The act of gaining unauthorised access to a computer system or network.
• Denial of Service (DoS) Attack: An attempt to make a machine or network resource unavailable to its intended users, typically by flooding the target with a huge volume of traffic. A Distributed Denial of Service (DDoS) attack uses a 'botnet' (a network of many compromised computers) to generate the traffic, making it much harder to stop.

To protect against cyber threats, a range of security solutions can be used. This is often called 'defence in depth', as no single solution is perfect.

• Authentication: This is the process of verifying you are who you say you are. Strong passwords are a first step, but better methods include two-factor authentication (2FA), which requires a second piece of information (like a code from your phone), and biometrics (using a unique physical trait like a fingerprint or face scan).
• Anti-malware Software: This software is designed to detect, prevent, and remove malicious software from your computer. It's vital to keep it updated to protect against new threats.
• Firewall: A firewall acts as a barrier between a trusted network (like your home network) and an untrusted network (like the internet). It monitors and filters incoming and outgoing traffic based on a set of security rules, blocking suspicious connections.
• Encryption: This is the process of scrambling data into an unreadable format (ciphertext). Only someone with the correct key can decrypt it back into its original form (plaintext). Encryption protects data both when it is stored (e.g., on your hard drive) and when it is transmitted (e.g., using HTTPS).
• Proxy Server: A proxy server acts as an intermediary between a user and the internet. It can be used to filter web content, hide the user's real IP address for anonymity, and cache frequently accessed pages to speed up browsing.