The internet and its uses

📌 Key points

1. The internet is the worldwide infrastructure of connected computers and networks; the World Wide Web is the collection of websites and web pages that are accessed using the internet.
2. A URL is the text address of a web page, made of the protocol (e.g. https), the domain name (e.g. www.example.com) and the file name or path (e.g. /news/index.html).
3. HTTP is the protocol used to transfer web pages; HTTPS is the secure version that encrypts data using SSL/TLS, shown by https and a padlock in the browser.
4. A web browser renders HTML to display web pages, and stores bookmarks, favourites and history, manages cookies, allows several tabs, and has navigation buttons and an address bar.
5. To find a web page, the browser sends the domain name to a DNS server, which finds the matching IP address (asking other DNS servers if needed) and returns it; the browser then requests the page from the web server at that IP address, which sends back the HTML.
6. Cookies are small text files a website stores on the user's device: session cookies are deleted when the browser is closed (e.g. a shopping basket), persistent cookies stay until an expiry date (e.g. saved login details or preferences).
7. Digital currency exists only electronically. A blockchain is a decentralised, digital ledger of transactions; each block holds a hash of the previous block, so changing any block breaks the chain and is detected.
8. Threats: brute-force attack (trying every possible password), data interception (e.g. packet sniffing), DDoS (many infected computers flood a server with requests), hacking, phishing (fake emails), pharming (malicious code redirects users to a fake website) and social engineering (tricking people).
9. Malware: a virus attaches to a file and copies itself when run; a worm copies itself across networks without user action; a trojan horse is disguised as legitimate software; spyware records activity such as key presses; adware shows unwanted adverts; ransomware encrypts data and demands payment.
10. Protection: access levels, anti-malware, authentication (strong passwords, biometrics, two-step verification), automatic software updates, checking the spelling and tone of messages, checking URLs, firewalls, privacy settings, proxy servers and SSL.

📖 Key terms

URL

Uniform Resource Locator: the text-based address of a web page.

DNS

Domain Name System: servers that translate domain names into IP addresses.

Cookie

A small text file stored by a website on the user's device to remember information about them.

Blockchain

A decentralised digital ledger where each block of transactions is linked to the previous one by a hash.

Phishing

Sending fake emails that look genuine to trick users into giving personal details.

Pharming

Malicious code that redirects a user to a fake website even when they type the correct URL.

Firewall

Hardware or software that monitors traffic into and out of a network and blocks it if it breaks set rules.

Proxy server

A server that acts between a user and the internet, hiding the user's IP address and filtering requests.