Internet Systems, Protocols, and Cyber Security Study Guide

Internet and World Wide Web (WWW)

• Internet Definition: A global system of interconnected computer networks that uses the Internet Protocol Suite ($TCP/IP$) to communicate between varied networks and devices.
• World Wide Web (WWW) Definition: A specific service that runs on the Internet. It provides access to web pages linked together using a hypertext system.
• Key Differences between Internet and WWW:
  • The Internet: A worldwide collection of interconnected networks and devices. It uses transmission protocols $TCP$ and Internet Protocol ($IP$). It allows for functionalities beyond web browsing, such as sending/receiving emails and online chatting (via text, audio, and video).
  • The WWW: A collection of multimedia web pages and other information stored on websites. It uses the Internet to access specific information from web servers. Resources are accessed via web browsers using the $HTTP(S)$ protocol. Uniform Resource Locators ($URL$) are used to specify the exact location of web pages.

Uniform Resource Locators (URL)

• Definition: Text addresses used to access websites.
• Structure Format: Protocol :// website address / path / file name or Protocol :// website address / file name.
• Example Breakdown (https://www.hoddereducation.co.uk/ict):
  • Protocol: https
  • Website Address: www.hoddereducation.co.uk
    • Host Name: www
    • Domain Name: hoddereducation
    • Domain Type: .co (Others include .com, .org, .edu, .net, .gov)
    • Country Code: .uk (Others include .mm)
  • Path: /ict

HTTP and HTTPS Protocols

• Hyper Text Transfer Protocol (HTTP): A set of rules that must be obeyed when transferring web pages across the internet.
• Hypertext Transfer Protocol Secure (HTTPS):
  • Uses $SSL$ (Secure Sockets Layer) or $TLS$ (Transport Layer Security).
  • Employs encryption methods to transfer data securely.
  • Used specifically for the transfer of private or sensitive data.

Web Browsers and Domain Name Service (DNS)

• Web Browser: Software that allows a user to display a web page on a computer screen. It interprets or translates $HTML$ code and displays the result.
  • Common Features: Storing favorite websites/bookmarks, keeping history of visited sites, backward/forward navigation, multi-tab support, and utilization of cookies.
• Domain Name Service (DNS): An internet service that translates human-readable domain names into numerical $IP$ addresses.
  • Mechanism: DNS is a network of servers. If one server cannot translate a name, it asks another until the correct $IP$ address is retrieved.

Retrieval and Location of Web Pages

• The Retrieval Process:
  1. User opens a browser and types a $URL$ (e.g., www.hoddereducation.co.uk). The browser asks a DNS server for the corresponding $IP$ address.
  2. If DNS Server 1 cannot find the $URL$ in its cache or database, it sends a request to DNS Server 2.
  3. DNS Server 2 finds the $URL$, maps it to the $IP$ address, and sends it back to DNS Server 1.
  4. DNS Server 1 passes the $IP$ address to the web browser.
  5. The web browser sends a request to the web server at that $IP$ address for the web page. The server sends the page back, and the browser renders the $HTML$ to display it.

Hyper Text Markup Language (HTML)

• Definition: The markup language used to create and develop web pages.
• Two Fundamental Components:
  • Structure: The layout of the web page. Includes placement of text and images, margins, line breaks, and padding.
  • Presentation: The formatting and style of the page. Includes font color, style, and size, background colors, image sizes, and border properties.

Cookies

• General Definition: A text file or program stored on a user's computer by a web browser. It is generated by a website and sent by a web server.
• Functionality: It collects key information about user visits and preferences. It functions as a lookup table with key-data pairs (e.g., username, John).
• Types of Cookies:
  • Session Cookie: Stored temporarily in memory; deleted when the browser is closed or the session ends. Used for virtual shopping baskets.
  • Persistent Cookie: Stored on the user's hard disk drive. Only deleted when an expiry date is reached or the user deletes it manually. Used to store login details and personal preferences.
• Purposes of Cookies: Remembering passwords/emails, recognizing returning users, saving shopping carts, tracking internet habits/histories, targeting advertising, and facilitating online financial transactions.

Digital Currency and Cryptocurrency

• Digital Currency: Currencies accessible only via computers or mobile phones (electronic form). Transactions are regulated by a central banking system. Centralization poses risks to confidentiality and security.
• Cryptocurrency: A digital/virtual currency using cryptography for security.
  • Decentralized: No central issuing or regulating authority; rules are set by the community.
  • Transparency: All transactions are publicly available and tracked; the total money in the system is monitored.
  • Blockchain Integration: Operates within a blockchain network for enhanced security.

Blockchain Technology

• Definition: A decentralized database or digital ledger consisting of interconnected computers not linked to a central server.
• Data Integrity: Transaction data is stored on all computers. New transactions create new blocks with a unique hash value and timestamp. Changes require consent from all network members, reducing hacking risks.
• The Chain: Blocks are linearly connected by storing the previous hash value. Block 1 is the "Genesis block" (no previous block).
• Hash Sensitivity: Changing data in a block changes its hash value, making subsequent blocks invalid and breaking the chain.
• Proof-of-work: An algorithm used to confirm transactions and produce new blocks. "Miners" (special users) complete these tasks for rewards.

Cyber Security Threats

• Brute Force Attack: A trial-and-error method to crack passwords by trying all combinations of characters. Prevention includes strong passwords and IDs.
• Data Interception: Attempting to eavesdrop on networks using packet sniffing (examining data packets) or wardriving (using laptops/GPS/antennas outside buildings to intercept Wi-Fi). Prevention includes encryption ($WEP$), complex passwords, and firewalls.
• Denial of Service (DoS): Flooding a server with thousands of requests to prevent legitimate access.
  • DDoS (Distributed Denial of Service): Spam traffic originates from many different computers.
  • Prevention: Use firewalls to restrict traffic and email filters for spam.
• Hacking: Gaining illegal access to a computer system without consent.
  • Ethical Hacking: Paid professionals authorized by companies to test system robustness.
  • Note: Encryption does not stop hacking; it makes data useless if stolen, but hackers can still delete or corrupt it.
• Malicious Software (Malware):
  • Virus: Replicates itself to delete/corrupt data; requires an active host program.
  • Worm: Standalone virus that replicates to search for network security weaknesses; does not need a host program.
  • Trojan Horse: Malicious program disguised as legitimate software; must be executed by the user to provide backdoors for cybercriminals.
  • Spyware/Key-logging: Secretly records key presses and sends data to the originator.
  • Adware: Floods computers with unwanted advertising/pop-ups; can hijack browsers.
  • Ransomware: Encrypts user data and demands a ransom for the decryption key.
• Phishing: Sending legitimate-looking emails to trick users into visiting fake websites to enter personal data.
• Pharming: Installing malicious code on a hard drive or web server to redirect users to fake websites. This often involves "DNS cache poisoning" (altering $IP$ addresses on a DNS server).
• Social Engineering: Manipulating people into breaking security procedures by exploiting fear, curiosity, empathy, or trust. It follows four stages: Identification, Targeting, Execution, and Covering Tracks.

Accidental Data Damage

• Causes: Human error, hardware failure, software failure, and natural disasters like floods or fires.
• Safeguards: Regular backups to cloud/other devices, frequent saving, correct shutdown procedures, and Use of Uninterruptible Power Supplies ($UPS$).

Security Systems and Measures

• Access Levels: Defining hierarchies (Read, Write, Delete). In social networks, levels include Public, Friends, Custom, and Data Owner.
• Anti-malware/Anti-spyware: Software that detects and removes malicious programs, blocks access to microphones/webcams, and may encrypt keystrokes.
• Authentication: Proving identity via something the user knows (passwords), has (secure token/SMS), or is (biometrics).
• Biometric Authentication:
  • Fingerprint scans: Developed, easy to use; can be intrusive or fail if skin is dirty.
  • Retina scans: High accuracy, no known replication; intrusive and expensive.
  • Face recognition: Non-intrusive; affected by lighting, hair, or glasses.
  • Voice recognition: Low cost; affected by illness (cold) and can be recorded for unauthorized access.
• Two-step Verification: Requires two factors (e.g., password + SMS code/biometric).
• Firewall: Sits between the computer and an external network. It filters traffic based on rules, logs activity, and warns of security issues. It cannot prevent employee misconduct or if the user disables it.
• Proxy Server: Acts as an intermediary web server. It filters traffic, hides the internal server's $IP$, and uses a cache to speed up website access.
• SSL and TLS (Security Protocols):
  • SSL: Uses certificates to establish trust. The browser checks the certificate from the server before starting an encrypted session.
  • TLS: An improvement on SSL. Comprised of the Record Protocol (handles data/encryption) and Handshake Protocol (authenticates client and server).
• Privacy Settings: Browser and app controls to limit profile access, opt-out of ads, and disable location tracking.
• Automatic Updates: Vital for installing security patches against malware and fixing bugs.

Verifying Communications and URLs

• Indicators of Scams: Bad grammar, suspicious tone, and misspelled domain names (e.g., gougle.com - known as typo squatting).
• Verification Steps: Check if the email address matches the company domain (avoiding @gmail.com for official business), look for https and the green padlock, and verify that destination links match the context of the email.