CSF Year 1 Semester 1: Networking Basics and Security

Networking Basics

• A network is a set of technologies used to connect computers together, allowing them to communicate and share resources.
• A typical network is a Local Area Network (LAN) that spans a small geographic area such as a home, a floor within a building, or a single building or multiple buildings in a campus.

Types of Computer Networks

• A LAN uses a network device (e.g., switch) to provide connection points for computers and devices using cables.
• A Wireless LAN (WLAN) allows devices to connect together using a Wireless Access Point, forming a larger LAN.
• A Wide Area Network (WAN) connects LANs over a wide geographical area, requiring a networking device called a Router.

Networking Hardware Components

• In a typical LAN, the networking hardware components are:
  • A network device (interconnecting device), typically a switch.
  • A network adapter or network interface controller (NIC) for each computer/device.
  • Network cables to connect the computers/devices to the switch.

MAC Addressing

• Each device has a MAC address (media access control address) that allows devices to communicate within a LAN.
• MAC addresses are physical hardware addresses burnt-in to the NIC.
• You can find your device's MAC address by typing the command ipconfig /all at the command prompt.

IP Addressing

• IP addresses identify each device connected to the Internet.
• Examples of well-known ports:
  • HTTP port number: 80.
  • FTP port number: 21.
  • Secure Shell port number: 22.
  • Telnet port number: 23.
  • DNS port number: 53.
  • HTTPS port number: 443.

Network Security Tools

• A network firewall is a system designed to prevent unauthorized access from entering the private network by filtering information from the Internet.

Network Firewall

• A Packet filtering firewall uses a set of individual instructions to control actions (Rule-based firewall):
  • Allow (let packet pass through).
  • Deny (drop packet).
  • Prompt (ask what action to take).
• Rules are evaluated from top down, and once a rule is matched, no further rules will be evaluated.

IDS and IPS

• Intrusion Detection System (IDS):
  • Monitors network for possible dangerous activity, including malicious acts and violations of security protocols.
  • Alerts the administrator when a problem is detected, but doesn't necessarily take any other action.
• Intrusion Prevention System (IPS):
  • Begins with intrusion detection, but can go one step further and act to stop ongoing and future attacks.
  • Can reject data packets or give commands to a firewall for action when an attack is detected.