Computer Networks and Cyber Security Fundamentals

Types of Network

• A network is two or more devices connected to share resources.
• Three main types:
  • Local Area Network (LAN): Small geographical area (under 1 mile). Hardware owned by the user.
  • Wide Area Network (WAN): Large geographical area (over 1 mile). Collection of LANs connected via routers. Hardware not always owned by the user.
  • Personal Area Network (PAN): Short range (10 metres). Bluetooth is common.
• Advantages of networks:
  • Resource sharing (printers, internet).
  • File access from any computer.
  • Easier communication (email, social networks).
  • Centralized backups and security.
• Disadvantages of networks:
  • Increased security risks.
  • Malicious software.
  • Central point of failure (servers, switches).
  • Performance impacted by users and data load.

Wired & Wireless Networks

• Wired Networks:
  • Use physical cables to connect devices.
  • Common types: Ethernet, Fiber optic, Copper
  • Ethernet: Carries electrical signals, common in offices and homes.
  • Fiber Optic: Uses light, higher speed and bandwidth, secure, long distance.
  • Copper: Traditional phone networks, slower, lower bandwidth, susceptible to interference.
• Wireless Networks:
  • Use radio waves.
  • Common types: Wi-Fi, Bluetooth
  • Wi-Fi: Connects devices to a wireless access point (WAP).
  • Bluetooth: Direct connection between two devices.
• Advantages & Disadvantages of Wired Networks:
  • Advantages: Fast, secure, high range.
  • Disadvantages: Not portable, costly, safety hazards.
• Advantages & Disadvantages of Wireless Networks:
  • Advantages: Portable, less expensive.
  • Disadvantages: Slower, less secure, relies on signal strength.

LAN Topologies

• Network topology: Physical structure of the network.
• Star Topology:
  • Central switch connecting all devices.
  • Advantages: If a cable fails, the rest of the network works.
  • Disadvantages: The central switch is a single point of failure.
• Bus Topology:
  • All devices connected by one single cable.
  • Advantages: Easy and cheap to set up.
  • Disadvantages: Low security, slow data transfer, whole network affected if the cable breaks.

Network Protocols

• Protocol: Set of rules governing communication on a network.
• Examples:
  • Ethernet & Wi-Fi: Data communication on LANs.
  • TCP/IP & UDP: Communication over WANs.
    • $TCP$ (Transmission Control Protocol): Ensures error-free communication between routers.
    • $IP$ (Internet Protocol): Delivers data to the right device.
    • $UDP$ (User Datagram Protocol): Alternative to $TCP$, faster but less secure.
  • HTTP & HTTPS: Communication between clients and servers for website viewing.
    • $HTTPS$: Encrypted version of $HTTP$.
  • FTP: File transfer between computers.
  • IMAP & SMTP: Handling sending and receiving email.
    • $SMTP$ (Simple Mail Transfer Protocol): Communication between email sender and server.
    • $IMAP$ (Internet Message Access Protocol): Downloading emails to a device.

Network Security

• Cyber security: Protecting networks, computers, programs, and data from attack.
• Main threats:
  • Social engineering.
  • Malicious code (malware).
  • Pharming.
  • Weak and default passwords.
  • Misconfigured access rights.
  • Removable media.
  • Unpatched and/or outdated software.
• Authentication: Using credentials to verify user identity.
• Encryption: Converting plain text into ciphered text.
• Firewalls: Barrier between a network and the internet.
• MAC address filtering: Limiting network access based on device MAC addresses.

The Concept of Layers

• Layer: A sub part of a more complex task.
• Advantages of layers:
  • Easier managing, repairing, and upgrading.
  • Focus on specific parts without affecting others.
  • Promotes data exchange (interoperability).
• TCP/IP Model: $4$-layer model for data transmission on the Internet.
  • Application: Software like web browsers.
  • Transport: Communication between two hosts. Protocols: $TCP$, $UDP$
  • Internet: Addresses and packages data. Protocol: $IP$
  • Link: Physical network hardware. Also known as ‘network access layer’ or ‘network interface layer’

Methods of Preventing Cyber Security Threats

• Penetration Testing: Attempting to gain unauthorized access to test security.
  • Malicious insider (white-box): Tester has some knowledge of the system.
  • External attack: Tester has no knowledge of the system.
• Biometric Measures: Using personal characteristics to identify users.
• CAPTCHA: Testing if a request is from a human or a bot.
• Confirming Identity: Checking email address validity.
• Automatic Software Updates: Keeping software updated automatically.