Computer Networks

Computer Networks

• A network involves interconnected devices communicating to share resources and information
• LAN is a local area network
• WLAN is a wireless local area network
• WAN is a wide area network

Network Devices

• Routers forward traffic between multiple networks
• Switches connect devices within a network domain and manage data transmission
• Access Points broadcast network signals to connect wireless devices
• Servers run applications and services and respond to client requests
• Firewalls monitor and filter traffic between local and external networks

Network Protocols

• TCP/IP governs data transmission over the internet
• SSL/TLS are cryptographic protocols that ensure secure communication over computer networks
• DNS translates DNS names to IP addresses and vice versa
• SSH is used for secure remote access to network devices

Communication Media

• Twisted Pair Cable includes two conductors twisted to improve electromagnetic compatibility.
• Fiber transmits data as light signals through thin strands of glass or plastic
• Wireless (Wi-Fi) enables networking for local devices, operating on frequency bands like 2.4 GHz and 5 GHz

Threats to Networks

• Man-in-the-Middle (MITM) Attacks include eavesdropping, session hijacking, SSL stripping, and ARP poisoning
• Denial-of-Service (DoS) and Distributed Denial-of-Service (DDoS) Attacks exist
• DNS Spoofing & Poisoning compromises network security

Layer 2 Security

• Layer 2 processes raw data transmission from the physical layer and transmits it to the network layer
• Layer 2 security protects the data link layer in network communications

ARP Spoofing

• Attackers use tools like Arpspoof or Driftnet to send forged ARP responses

CAM Table Overflow

• A hacker connects to switch ports and uses a program to mimic thousands of MAC addresses

MAC Spoofing

• Media Access Control (MAC) Spoofing involves an attacker altering the MAC address of their device to mimic another on the network
• One technique involves replicating a legitimate device’s MAC address for masquerading purposes
• The other technique involves randomizing a MAC address and using it to impersonate a network device

DHCP Spoofing

• An attack where a hacker places a rogue DHCP server on a network
• The fastest DHCP server will receive the first request when a client accesses the network and requests an address
• The rogue server responds and assigns an address, gaining control over the device's gateway

DNS Spoofing & Poisoning

• DNS Poisoning is a type of DNS Spoofing

Wi-Fi Security

• Wi-Fi is prone to interception and unauthorized access due to its use of radio waves for data transmission
• Security protocols and encryption are common methods to protect Wi-Fi networks

Wi-Fi Security Protocols

• These protocols provide encryption and authentication for Wi-Fi networks
• Wired Equivalent Privacy (WEP) was the standard wireless network security method until 2004 using basic 64-/128-bit encryption, now considered insecure
• WPA (Wi-Fi Protected Access) uses 128-/256-bit encryption and Temporal Key Integrity Protocol (TKIP)
• WPA2 is an improved version of WPA, offering advanced network security through AES, commonly used in enterprise and home networks
• WPA3 is more secure, supports 192-/256-/384-bit encryption options, and supports Wi-Fi 6 networks

Wi-Fi Authentication Methods

• Password-based authentication: An encrypted password is sent to the router for verification against stored credentials
• Certificate-based authentication: Uses digital certificates for higher security to identify and authenticate users or devices
• 802.1X: Uses a RADIUS server to authenticate users, is a standard for network access control, and is often used in enterprise environments

Network Security Measures

• Encryption secures data
• Virtual Private Networks (VPNs) create secure connections
• Firewalls monitor and control network traffic
• Intrusion Prevention Systems (IPS) and Intrusion Detection Systems (IDS) identify and prevent malicious activity
• Rate limiting controls traffic flow
• Network segmentation divides a network into smaller networks